Contention-based data transmissions on return link

ABSTRACT

Methods and apparatuses are disclosed for a user terminal (UT) to transmit data to a network controller via a satellite in a satellite system. The UT may begin transmitting, during a time period, a first portion of the data using contention-based resources of the satellite system prior to receiving a grant of scheduled return link resources of the satellite system. The UT may also transmit, on the contention-based resources, a buffer status report (BSR) during the time period. The UT may terminate data transmissions on the contention-based resources after an expiration of the time period or upon receiving the grant of scheduled return link resources. After receiving the grant, the UT may transmit a second portion of the data on the scheduled return link resources.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119(e) to commonly ownedU.S. Provisional Patent Application No. 62/288,336 entitled“CONTENTION-BASED DATA TRANSMISSIONS ON RETURN LINK” filed on Jan. 28,2016, the entirety of which is incorporated by reference herein.

INTRODUCTION

Various aspects described herein relate to satellite communications, andmore particularly to reducing transmission delays in a satellite system.

Conventional satellite-based communication systems include gateways andone or more satellites to relay communication signals between thegateways and one or more user terminals. A gateway is an Earth stationhaving an antenna for transmitting signals to, and receiving signalsfrom, communication satellites. A gateway provides communication links,using satellites, for connecting a user terminal to other user terminalsor users of other communication systems, such as a public switchedtelephone network, the internet and various public and/or privatenetworks. A satellite is an orbiting receiver and repeater used to relayinformation.

A satellite can receive signals from and transmit signals to a userterminal provided the user terminal is within the “footprint” of thesatellite. The footprint of a satellite is the geographic region on thesurface of the Earth within the range of signals of the satellite. Thefootprint is usually geographically divided into “beams,” through theuse of one or more antennas. Each beam covers a particular geographicregion within the footprint. Beams may be directed so that more than onebeam from the same satellite covers the same specific geographic region.

Geosynchronous satellites have long been used for communications. Ageosynchronous satellite is stationary relative to a given location onthe Earth, and thus there is little timing shift and frequency shift inradio signal propagation between a communication transceiver on theEarth and the geosynchronous satellite. However, because geosynchronoussatellites are limited to a geosynchronous orbit (GSO), the number ofsatellites that may be placed in the GSO is limited. As alternatives togeosynchronous satellites, communication systems which utilize aconstellation of satellites in non-geosynchronous orbits (NGSO), such aslow-earth orbits (LEO), have been devised to provide communicationcoverage to the entire Earth or at least large parts of the Earth.

Although NGSO satellites (e.g., LEO satellites) orbit the Earth at muchlower altitudes than GSO satellites, data transmission delays associatedwith NGSO satellite communications may degrade user experience,especially for real-time data such as voice and video data. Thus, thereis a need to reduce the data transmission delays associated with NGSOsatellite communications.

SUMMARY

Aspects of the disclosure are directed to apparatuses and methods forfacilitating communications in a satellite system. In someimplementations, a user terminal may transit data to a gateway via asatellite. In one example, a method of wireless communication performedby a user terminal in a satellite system is disclosed. The method mayinclude receiving data for transmission to a gateway via a satellite;receiving, from the gateway, an activation of contention-based resourcesof the satellite system; transmitting, during a time period, a firstportion of the data on a plurality of subframes of the contention-basedresources prior to receiving a grant of scheduled return link resources;and terminating data transmissions on the contention-based resourcesafter an expiration of the time period or upon receiving the grant ofscheduled return link resources, irrespective of collisions on thecontention-based resources.

In another example, a user terminal configured for wirelesscommunication in a satellite system is disclosed. The user terminal mayinclude one or more processors and a memory configured to storeinstructions. Execution of the instructions by the one or moreprocessors may cause the user terminal to receive data for transmissionto a gateway via a satellite; receive, from the gateway, an activationof contention-based resources of the satellite system; transmit, duringa time period, a first portion of the data on a plurality of subframesof the contention-based resources prior to receiving a grant ofscheduled return link resources; and terminate data transmissions on thecontention-based resources after an expiration of the time period orupon receiving the grant of scheduled return link resources,irrespective of collisions on the contention-based resources.

In another example, a user terminal configured for wirelesscommunication in a satellite system is disclosed. The user terminal mayinclude means for receiving data for transmission to a gateway via asatellite; means for receiving, from the gateway, an activation ofcontention-based resources of the satellite system; means fortransmitting, during a time period, a first portion of the data on aplurality of subframes of the contention-based resources prior toreceiving a grant of scheduled return link resources; and means forterminating data transmissions on the contention-based resources afteran expiration of the time period or upon receiving the grant ofscheduled return link resources, irrespective of collisions on thecontention-based resources.

In another example, a non-transitory computer-readable medium isdisclosed. The non-transitory computer-readable medium may storeinstructions that, when executed by one or more processors of a userterminal, cause the user terminal to perform operations that may includereceiving data for transmission to a gateway via a satellite; receiving,from the gateway, an activation of contention-based resources of thesatellite system; transmitting, during a time period, a first portion ofthe data on a plurality of subframes of the contention-based resourcessystem prior to receiving a grant of scheduled return link resources;and terminating data transmissions on the contention-based resourcesafter an expiration of the time period or upon receiving the grant ofscheduled return link resources, irrespective of collisions on thecontention-based resources.

In other implementations, a network controller may receive data from auser terminal via a satellite. In one example, a method of wirelesscommunication performed by a network controller in a satellite system isdisclosed. The method may include allocating contention-based resourcesof the satellite system to a plurality of user terminals (UTs);activating the allocated contention-based resources by transmitting anactivation signal to the plurality of UTs; receiving, from a first UTvia a satellite of the satellite system, a first portion of data on aplurality of subframes of the contention-based resources during a timeperiod; and suspending the allocation of the contention-based resourcesto the first UT after an expiration of the time period or upon a grantof scheduled return link resources to the first UT, irrespective ofcollisions on the contention-based resources.

In another example, a network controller configured for wirelesscommunication in a satellite system is disclosed. The network controllermay include one or more processors and a memory configured to storeinstructions. Execution of the instructions by the one or moreprocessors may cause the network controller to allocate contention-basedresources of the satellite system to a plurality of user terminals(UTs); activate the allocated contention-based resources by transmittingan activation signal to the plurality of UTs; receive, from a first UTvia a satellite of the satellite system, a first portion of data on aplurality of subframes of the contention-based resources during a timeperiod; and suspend the allocation of the contention-based resources tothe first UT after an expiration of the time period or upon a grant ofscheduled return link resources to the first UT, irrespective ofcollisions on the contention-based resources.

In another example, a non-transitory computer-readable medium isdisclosed. The non-transitory computer-readable medium may storeinstructions that, when executed by one or more processors of a networkcontroller, cause the network controller to perform operations that mayinclude allocating contention-based resources of the satellite system toa plurality of user terminals (UTs); activating the allocatedcontention-based resources by transmitting an activation signal to theplurality of UTs; receiving, from a first UT via a satellite of thesatellite system, a first portion of data on a plurality of subframes ofthe contention-based resources during a time period; and suspending theallocation of the contention-based resources to the first UT after anexpiration of the time period or upon a grant of scheduled return linkresources to the first UT, irrespective of collisions on thecontention-based resources.

In another example, a network controller configured for wirelesscommunication in a satellite system is disclosed. The network controllermay include means for allocating contention-based resources of thesatellite system to a plurality of user terminals (UTs); means foractivating the allocated contention-based resources by transmitting anactivation signal to the plurality of UTs; means for receiving, from afirst UT via a satellite of the satellite system, a first portion ofdata on a plurality of subframes of the contention-based resourcesduring a time period; and means for suspending the allocation of thecontention-based resources to the first UT after an expiration of thetime period or upon a grant of scheduled return link resources to thefirst UT, irrespective of collisions on the contention-based resources.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of this disclosure are illustrated by way of example and are notintended to be limited by the figures of the accompanying drawings.

FIG. 1 shows a block diagram of an example communication system.

FIG. 2 shows a block diagram of one example of the gateway of FIG. 1.

FIG. 3 shows a block diagram of one example of the satellite of FIG. 1.

FIG. 4 shows a block diagram of one example of the user terminal (UT) ofFIG. 1.

FIG. 5 shows a block diagram of one example of the user equipment (UE)of FIG. 1.

FIG. 6 shows a diagram depicting an NGSO satellite constellation and aGSO satellite constellation orbiting the earth.

FIG. 7 depicts an NGSO satellite transmitting a number of beams onto thesurface of the Earth.

FIG. 8A shows a timing diagram depicting an example operation fortransmitting data from a UT to a network controller via a satelliteusing return link resources granted by the network controller.

FIG. 8B shows a timing diagram depicting an example operation fortransmitting data from a UT to a network controller via a satelliteusing contention-based resources and return link resources granted bythe network controller.

FIG. 8C shows a timing diagram depicting another example operation fortransmitting data from a UT to a network controller via a satelliteusing contention-based resources and return link resources granted bythe network controller.

FIG. 9 shows a block diagram of an example UT in accordance with exampleimplementations.

FIG. 10 shows a block diagram of an example network controller inaccordance with example implementations.

FIG. 11A shows an illustrative flowchart depicting an example operationfor transmitting data from a UT to a network controller via a satelliteusing contention-based resources and return link resources granted bythe network controller.

FIG. 11B shows an illustrative flowchart depicting an example operationfor transmitting data from a UT to a network controller via a satelliteusing contention-based resources and return link resources granted bythe network controller.

FIG. 11C shows an illustrative flowchart depicting an example operationfor transmitting data from a UT to a network controller via a satelliteusing contention-based resources and re-transmitting, on return linkresources granted by the network controller, data associated withcollisions on the contention-based resources.

FIG. 12A shows an illustrative flowchart depicting an example operationfor receiving data from a UT via a satellite using contention-basedresources and return link resources granted by the network controller.

FIG. 12B shows an illustrative flowchart depicting an example operationfor receiving data from a UT via a satellite using contention-basedresources and return link resources granted by the network controller.

FIG. 12C shows an illustrative flowchart depicting an example operationfor receiving data from a UT via a satellite using contention-basedresources, detecting a collision on the contention-based resources, andrequesting re-transmission of data from an identified UT on return linkresources granted by the network controller.

FIG. 13 shows an example user terminal represented as a series ofinterrelated functional modules.

FIG. 14 shows an example network controller represented as a series ofinterrelated functional modules.

DETAILED DESCRIPTION

The example implementations described herein may reduce datatransmission delays associated with NGSO satellite communications. Asdescribed in more detail below, a user terminal having buffered data fortransmission to a gateway via one or more satellites of a satellitesystem may begin transmitting the data to the gateway usingcontention-based resources of the satellite system without an explicitgrant of scheduled return link resources of the satellite system. Theuser terminal may transmit, on the contention-based resources, ascheduling request for a grant of the scheduled return link resources.The user terminal may continue transmitting data on the contention-basedresources until the scheduled return link resources are granted to theuser terminal. Thereafter, the user terminal may transmit a remainingportion of the data (e.g., a second portion of the data) on thescheduled return link resources. Because the user terminal may begintransmitting data to the gateway prior to receiving the grant ofscheduled return link resources, data transmission delays may be reduced(e.g., as compared to conventional communication systems). Morespecifically, allowing the user terminal to begin transmitting dataprior to receiving a grant of scheduled return link resources may avoidscheduling request opportunity delays, signal propagation delaysassociated with requesting and receiving the grant of scheduled returnlink resources, and processing delays associated with the gateway,thereby minimizing data transmission delays associated with thesatellite system.

Aspects of the disclosure are described in the following description andrelated drawings directed to specific examples. Alternate examples maybe devised without departing from the scope of the disclosure.Additionally, well-known elements will not be described in detail orwill be omitted so as not to obscure the relevant details of thedisclosure.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects. Likewise, the term “aspects” does not require that allaspects include the discussed feature, advantage or mode of operation.

The terminology used herein is for the purpose of describing particularaspects only and is not intended to be limiting of the aspects. As usedherein, the singular forms “a,” “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” or “including,” when used herein, specify thepresence of stated features, integers, steps, operations, elements, orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components, orgroups thereof. Moreover, it is understood that the word “or” has thesame meaning as the Boolean operator “OR,” that is, it encompasses thepossibilities of “either” and “both” and is not limited to “exclusiveor” (“XOR”), unless expressly stated otherwise. It is also understoodthat the symbol “/” between two adjacent words has the same meaning as“or” unless expressly stated otherwise. Moreover, phrases such as“connected to,” “coupled to” or “in communication with” are not limitedto direct connections unless expressly stated otherwise.

Further, many aspects are described in terms of sequences of actions tobe performed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits, for example, central processing units (CPUs), graphicprocessing units (GPUs), digital signal processors (DSPs), applicationspecific integrated circuits (ASICs), field programmable gate arrays(FPGAs), or various other types of general purpose or special purposeprocessors or circuits, by program instructions being executed by one ormore processors, or by a combination of both. Additionally, thesesequence of actions described herein can be considered to be embodiedentirely within any form of computer readable storage medium havingstored therein a corresponding set of computer instructions that uponexecution would cause an associated processor to perform thefunctionality described herein. Thus, the various aspects of thedisclosure may be embodied in a number of different forms, all of whichhave been contemplated to be within the scope of the claimed subjectmatter. In addition, for each of the aspects described herein, thecorresponding form of any such aspects may be described herein as, forexample, “logic configured to” perform the described action.

In the following description, numerous specific details are set forthsuch as examples of specific components, circuits, and processes toprovide a thorough understanding of the present disclosure. The term“coupled” as used herein means connected directly to or connectedthrough one or more intervening components or circuits. Also, in thefollowing description and for purposes of explanation, specificnomenclature is set forth to provide a thorough understanding of thepresent disclosure. However, it will be apparent to one skilled in theart that these specific details may not be required to practice thevarious aspects of the present disclosure. In other instances,well-known circuits and devices are shown in block diagram form to avoidobscuring the present disclosure. The various aspects of the presentdisclosure are not to be construed as limited to specific examplesdescribed herein but rather to include within their scopes allimplementations defined by the appended claims.

FIG. 1 illustrates an example of a satellite communication system 100which includes a plurality of satellites (although only one satellite300 is shown for clarity of illustration) in non-geosynchronous orbits,for example, low-earth orbits (LEO), satellite access network (SAN) 150in communication with the satellite 300, a plurality of user terminals(UTs) 400 and 401 in communication with the satellite 300, and aplurality of user equipment (UE) 500 and 501 in communication with theUTs 400 and 401, respectively. Each UE 500 or 501 may be a user devicesuch as a mobile device, a telephone, a smartphone, a tablet, a laptopcomputer, a computer, a wearable device, a smart watch, an audiovisualdevice, or any device including the capability to communicate with a UT.Additionally, the UE 500 and/or UE 501 may be a device (e.g., accesspoint, small cell, etc.) that is used to communicate to one or more enduser devices. In the example illustrated in FIG. 1, the UT 400 and theUE 500 communicate with each other via a bidirectional access link(having a forward access link and return access link), and similarly,the UT 401 and the UE 501 communicate with each other via anotherbidirectional access link. In another implementation, one or moreadditional UE (not shown) may be configured to receive only andtherefore communicate with a UT only using a forward access link. Inanother implementation, one or more additional UE (not shown) may alsocommunicate with UT 400 or UT 401. Alternatively, a UT and acorresponding UE may be integral parts of a single physical device, suchas a mobile telephone with an integral satellite transceiver and anantenna for communicating directly with a satellite, for example.

The UT 400 may include a UT resource controller 421 that may allow theUT 400 to transmit buffered data to a gateway (e.g., gateway 200 orgateway 201) via a satellite (e.g., satellite 300) usingcontention-based resources of the satellite system 100. For at leastsome example implementations, the UT resource controller 421 may allowthe UT 400 to transmit, during a time period, a first portion ofbuffered data on contention-based resources allocated by the SAN 150prior to receiving a grant of scheduled return link resources. The UTresource controller 421 may also allow the UT 400 to transmit, duringthe time period, a request for the grant of scheduled return linkresources and/or a buffer status report on the contention-basedresources. In some aspects, the UT resource controller 421 may cause theUT 400 to terminate data transmissions on the contention-based resources(e.g., after expiration of the time period or after receiving the grantof scheduled return link resources). Upon receiving the grant of thescheduled RL resources, the UT resource controller 421 may allow the UT400 to transmit additional portions of the buffered data to the gateway200 or 201, via satellite 300, on the scheduled return link resourcesgranted by the SAN 150.

The SAN 150 may include gateways 200 and 201, infrastructure 106, andadditional components (not shown for simplicity) for communicating withthe satellite 300. The gateway 200 may have access to the Internet 108or one or more other types of public, semiprivate or private networks.In the example illustrated in FIG. 1, the gateway 200 is incommunication with infrastructure 106, which is capable of accessing theInternet 108 or one or more other types of public, semiprivate orprivate networks. The gateway 200 may also be coupled to various typesof communication backhaul, including, for example, landline networkssuch as optical fiber networks or public switched telephone networks(PSTN) 110. Further, in alternative implementations, the gateway 200 mayinterface to the Internet 108, PSTN 110, or one or more other types ofpublic, semiprivate or private networks without using infrastructure106. Still further, gateway 200 may communicate with other gateways,such as gateway 201 through the infrastructure 106 or alternatively maybe configured to communicate to gateway 201 without using infrastructure106. Infrastructure 106 may include, in whole or part, a network controlcenter (NCC), a satellite control center (SCC), a wired and/or wirelesscore network and/or any other components or systems used to facilitateoperation of and/or communication with the satellite communicationsystem 100. In some implementations, gateway 200 may include a UTresource allocator 252 that may allocate contention-based resources toone or more UTs (e.g., UTs 400 and 401), for example, as described inmore detail below with respect to FIG. 2.

Communications between the satellite 300 and the gateway 200 in bothdirections are called feeder links, whereas communications between thesatellite and each of the UTs 400 and 401 in both directions are calledservice links. A signal path from the satellite 300 to a ground station,which may be the gateway 200 or one of the UTs 400 and 401, may begenerically called a downlink. A signal path from a ground station tothe satellite 300 may be generically called an uplink. Additionally, asillustrated, signals can have a general directionality such as a forwardlink and a return link or reverse link. Accordingly, a communicationlink in a direction originating from the gateway 200 and terminating atthe UT 400 through the satellite 300 is called a forward link, whereas acommunication link in a direction originating from the UT 400 andterminating at the gateway 200 through the satellite 300 is called areturn link or reverse link. As such, the signal path from the gateway200 to the satellite 300 is labeled “Forward Feeder Link” whereas thesignal path from the satellite 300 to the gateway 200 is labeled “ReturnFeeder Link” in FIG. 1. In a similar manner, the signal path from eachUT 400 or 401 to the satellite 300 is labeled “Return Service Link”whereas the signal path from the satellite 300 to each UT 400 or 401 islabeled “Forward Service Link” in FIG. 1.

FIG. 2 is an example block diagram of gateway 200, which also can applyto gateway 201 of FIG. 1. Gateway 200 is shown to include a number ofantennas 205, an RF subsystem 210, a digital subsystem 220, a PublicSwitched Telephone Network (PSTN) interface 230, a Local Area Network(LAN) interface 240, a gateway interface 245, and a gateway controller250. RF subsystem 210 is coupled to antennas 205 and to digitalsubsystem 220. Digital subsystem 220 is coupled to PSTN interface 230,to LAN interface 240, and to gateway interface 245. Gateway controller250 is coupled to RF subsystem 210, digital subsystem 220, PSTNinterface 230, LAN interface 240, and gateway interface 245.

RF subsystem 210, which may include a number of RF transceivers 212, anRF controller 214, and an antenna controller 216, may transmitcommunication signals to satellite 300 via a forward feeder link 301F,and may receive communication signals from satellite 300 via a returnfeeder link 301R. Although not shown for simplicity, each of the RFtransceivers 212 may include a transmit chain and a receive chain. Eachreceive chain may include a low noise amplifier (LNA) and adown-converter (e.g., a mixer) to amplify and down-convert,respectively, received communication signals in a well-known manner. Inaddition, each receive chain may include an analog-to-digital converter(ADC) to convert the received communication signals from analog signalsto digital signals (e.g., for processing by digital subsystem 220). Eachtransmit chain may include an up-converter (e.g., a mixer) and a poweramplifier (PA) to up-convert and amplify, respectively, communicationsignals to be transmitted to satellite 300 in a well-known manner. Inaddition, each transmit chain may include a digital-to-analog converter(DAC) to convert the digital signals received from digital subsystem 220to analog signals to be transmitted to satellite 300.

The RF controller 214 may be used to control various aspects of thenumber of RF transceivers 212 (e.g., selection of the carrier frequency,frequency and phase calibration, gain settings, and the like). Theantenna controller 216 may control various aspects of the antennas 205(e.g., beamforming, beam steering, gain settings, frequency tuning, andthe like).

The digital subsystem 220 may include a number of digital receivermodules 222, a number of digital transmitter modules 224, a baseband(BB) processor 226, and a control (CTRL) processor 228. Digitalsubsystem 220 may process communication signals received from RFsubsystem 210 and forward the processed communication signals to PSTNinterface 230 and/or LAN interface 240, and may process communicationsignals received from PSTN interface 230 and/or LAN interface 240 andforward the processed communication signals to RF subsystem 210.

Each digital receiver module 222 may correspond to signal processingelements used to manage communications between gateway 200 and UT 400.One of the receive chains of RF transceivers 212 may provide inputsignals to multiple digital receiver modules 222. A number of digitalreceiver modules 222 may be used to accommodate all of the satellitebeams and possible diversity mode signals being handled at any giventime. Although not shown for simplicity, each digital receiver module222 may include one or more digital data receivers, a searcher receiver,and a diversity combiner and decoder circuit. The searcher receiver maybe used to search for appropriate diversity modes of carrier signals,and may be used to search for pilot signals (or other relatively fixedpattern strong signals).

The digital transmitter modules 224 may process signals to betransmitted to UT 400 via satellite 300. Although not shown forsimplicity, each digital transmitter module 224 may include a transmitmodulator that modulates data for transmission. The transmission powerof each transmit modulator may be controlled by a corresponding digitaltransmit power controller (not shown for simplicity) that may (1) applya minimum level of power for purposes of interference reduction andresource allocation and (2) apply appropriate levels of power whenneeded to compensate for attenuation in the transmission path and otherpath transfer characteristics.

The control processor 228, which is coupled to digital receiver modules222, digital transmitter modules 224, and baseband processor 226, mayprovide command and control signals to effect functions such as, but notlimited to, signal processing, timing signal generation, power control,handoff control, diversity combining, and system interfacing.

The control processor 228 may also control the generation and power ofpilot, synchronization, and paging channel signals and their coupling tothe transmit power controller (not shown for simplicity). The pilotchannel is a signal that is not modulated by data, and may use arepetitive unchanging pattern or non-varying frame structure type(pattern) or tone type input. For example, the orthogonal function usedto form the channel for the pilot signal generally has a constant value,such as all 1's or 0's, or a well-known repetitive pattern, such as astructured pattern of interspersed 1's and 0's.

Baseband processor 226 is well known in the art and is therefore notdescribed in detail herein. For example, the baseband processor 226 mayinclude a variety of known elements such as (but not limited to) coders,data modems, and digital data switching and storage components.

The PSTN interface 230 may provide communication signals to, and receivecommunication signals from, an external PSTN either directly or throughadditional infrastructure 106, as illustrated in FIG. 1. The PSTNinterface 230 is well known in the art, and therefore is not describedin detail herein. For other implementations, the PSTN interface 230 maybe omitted, or may be replaced with any other suitable interface thatconnects gateway 200 to a ground-based network (e.g., the Internet).

The LAN interface 240 may provide communication signals to, and receivecommunication signals from, an external LAN. For example, LAN interface240 may be coupled to the internet 108 either directly or throughadditional infrastructure 106, as illustrated in FIG. 1. The LANinterface 240 is well known in the art, and therefore is not describedin detail herein.

The gateway interface 245 may provide communication signals to, andreceive communication signals from, one or more other gatewaysassociated with the satellite communication system 100 of FIG. 1 (and/orto/from gateways associated with other satellite communication systems,not shown for simplicity). For some implementations, gateway interface245 may communicate with other gateways via one or more dedicatedcommunication lines or channels (not shown for simplicity). For otherimplementations, gateway interface 245 may communicate with othergateways using PSTN 110 and/or other networks such as the Internet 108(see also FIG. 1). For at least one implementation, gateway interface245 may communicate with other gateways via infrastructure 106.

Overall gateway control may be provided by gateway controller 250. Thegateway controller 250 may plan and control utilization of satellite300's resources by gateway 200. For example, the gateway controller 250may analyze trends, generate traffic plans, allocate satelliteresources, monitor (or track) satellite positions, and monitor theperformance of gateway 200 and/or satellite 300. The gateway controller250 may also be coupled to a ground-based satellite controller (notshown for simplicity) that maintains and monitors orbits of satellite300, relays satellite usage information to gateway 200, tracks thepositions of satellite 300, and/or adjusts various channel settings ofsatellite 300.

For the example implementation illustrated in FIG. 2, the gatewaycontroller 250 includes a local time, frequency, and position references251, which may provide local time and frequency information to the RFsubsystem 210, the digital subsystem 220, and/or the interfaces 230,240, and 245. The time and frequency information may be used tosynchronize the various components of gateway 200 with each other and/orwith satellite(s) 300. The local time, frequency, and positionreferences 251 may also provide position information (e.g., ephemerisdata) of satellite(s) 300 to the various components of gateway 200.Further, although depicted in FIG. 2 as included within gatewaycontroller 250, for other implementations, the local time, frequency,and position references 251 may be a separate subsystem that is coupledto gateway controller 250 (and/or to one or more of digital subsystem220 and RF subsystem 210).

Although not shown in FIG. 2 for simplicity, the gateway controller 250may also be coupled to a network control center (NCC) and/or a satellitecontrol center (SCC). For example, the gateway controller 250 may allowthe SCC to communicate directly with satellite(s) 300, for example, toretrieve ephemeris data from satellite(s) 300. The gateway controller250 may also receive processed information (e.g., from the SCC and/orthe NCC) that allows gateway controller 250 to properly aim its antennas205 (e.g., at the appropriate satellite(s) 300), to schedule beamtransmissions, to coordinate handovers, and to perform various otherwell-known functions.

Gateway controller 250 may include or otherwise be associated with a UTresource allocator 252 that may allocate contention-based resources toone or more UTs and/or may control or assist with granting scheduledreturn link resources to the one or more UTs. More specifically, the UTresource allocator 252 may allocate contention-based resources to aplurality of UTs, for example, so that the UTs may transmit buffereddata to gateway 200 via satellite 300 prior to a grant of scheduledreturn link resources to the UTs. The gateway 200 may receive a firstportion of buffered data from a UT on the contention-based resources. Insome aspects, reception of the data by the SAN on the contention-basedresources may serve as an implicit scheduling request, from the UT, fora grant of scheduled return link resources. The gateway 200 may alsoreceive a buffer status report (BSR) on the contention-based resources.In some aspects, the UT resource allocator 252 may suspend or terminatethe allocation of contention-based resources after expiration of a timeperiod. In other aspects, the UT resource allocator 252 may suspend orterminate the allocation of contention-based resources in response tothe grant of scheduled return link resources to the UT.

For some implementations, the UT resource allocator 252 may also includea scheduler (not shown in FIG. 2 for simplicity) that schedules one ormore grants of return link resources to the UTs. Upon receiving a grantof scheduled return link resources, a UT may transmit a second portion(e.g., a remaining portion) of the buffered data on the scheduled returnlink resources of the satellite system 100. After the allocation ofcontention-based resources is suspended or terminated, the UT resourceallocator 252 may subsequently allocate contention-based resources tothe UTs, for example, when the UTs receive additional data fortransmission to the gateway 200 via satellite 300. For otherimplementations, the scheduler may be included in other suitablecomponents of the gateway 200, and/or may be included within othersuitable components of the SAN 150 (see also FIG. 1).

FIG. 3 is an example block diagram of satellite 300 for illustrativepurposes only. It will be appreciated that specific satelliteconfigurations can vary significantly and may or may not includeon-board processing. Further, although illustrated as a singlesatellite, two or more satellites using inter-satellite communicationmay provide the functional connection between the gateway 200 and UT400. It will be appreciated that disclosure is not limited to anyspecific satellite configuration and any satellite or combinations ofsatellites that can provide the functional connection between thegateway 200 and UT 400 can be considered within the scope of thedisclosure. In one example, satellite 300 is shown to include a forwardtransponder 310, a return transponder 320, an oscillator 330, acontroller 340, forward link antennas 351-352, and return link antennas361-362. The forward transponder 310, which may process communicationsignals within a corresponding channel or frequency band, may include arespective one of first bandpass filters 311(1)-311(N), a respective oneof first LNAs 312(1)-312(N), a respective one of frequency converters313(1)-313(N), a respective one of second LNAs 314(1)-314(N), arespective one of second bandpass filters 315(1)-315(N), and arespective one of PAs 316(1)-316(N). Each of the PAs 316(1)-316(N) iscoupled to a respective one of antennas 352(1)-352(N), as shown in FIG.3.

Within each of the respective forward paths FP(1)-FP(N), the firstbandpass filter 311 passes signal components having frequencies withinthe channel or frequency band of the respective forward path FP, andfilters signal components having frequencies outside the channel orfrequency band of the respective forward path FP. Thus, the pass band ofthe first bandpass filter 311 corresponds to the width of the channelassociated with the respective forward path FP. The first LNA 312amplifies the received communication signals to a level suitable forprocessing by the frequency converter 313. The frequency converter 313converts the frequency of the communication signals in the respectiveforward path FP (e.g., to a frequency suitable for transmission fromsatellite 300 to UT 400). The second LNA 314 amplifies thefrequency-converted communication signals, and the second bandpassfilter 315 filters signal components having frequencies outside of theassociated channel width. The PA 316 amplifies the filtered signals to apower level suitable for transmission to UTs 400 via respective antenna352. The return transponder 320, which includes a number N of returnpaths RP(1)-RP(N), receives communication signals from UT 400 alongreturn service link 302R via antennas 361(1)-361(N), and transmitscommunication signals to gateway 200 along return feeder link 301R viaone or more antennas 362. Each of the return paths RP(1)-RP(N), whichmay process communication signals within a corresponding channel orfrequency band, may be coupled to a respective one of antennas361(1)-361(N), and may include a respective one of first bandpassfilters 321(1)-321(N), a respective one of first LNAs 322(1)-322(N), arespective one of frequency converters 323(1)-323(N), a respective oneof second LNAs 324(1)-324(N), and a respective one of second bandpassfilters 325(1)-325(N).

Within each of the respective return paths RP(1)-RP(N), the firstbandpass filter 321 passes signal components having frequencies withinthe channel or frequency band of the respective return path RP, andfilters signal components having frequencies outside the channel orfrequency band of the respective return path RP. Thus, the pass band ofthe first bandpass filter 321 may for some implementations correspond tothe width of the channel associated with the respective return path RP.The first LNA 322 amplifies all the received communication signals to alevel suitable for processing by the frequency converter 323. Thefrequency converter 323 converts the frequency of the communicationsignals in the respective return path RP (e.g., to a frequency suitablefor transmission from satellite 300 to gateway 200). The second LNA 324amplifies the frequency-converted communication signals, and the secondbandpass filter 325 filters signal components having frequencies outsideof the associated channel width. Signals from the return pathsRP(1)-RP(N) are combined and provided to the one or more antennas 362via a PA 326. The PA 326 amplifies the combined signals for transmissionto the gateway 200.

Oscillator 330, which may be any suitable circuit or device thatgenerates an oscillating signal, provides a forward local oscillatorsignal LO(F) to the frequency converters 313(1)-313(N) of forwardtransponder 310, and provides a return local oscillator signal LO(R) tofrequency converters 323(1)-323(N) of return transponder 320. Forexample, the LO(F) signal may be used by frequency converters313(1)-313(N) to convert communication signals from a frequency bandassociated with the transmission of signals from gateway 200 tosatellite 300 to a frequency band associated with the transmission ofsignals from satellite 300 to UT 400. The LO(R) signal may be used byfrequency converters 323(1)-323(N) to convert communication signals froma frequency band associated with the transmission of signals from UT 400to satellite 300 to a frequency band associated with the transmission ofsignals from satellite 300 to gateway 200.

Controller 340, which is coupled to forward transponder 310, returntransponder 320, and oscillator 330, may control various operations ofsatellite 300 including (but not limited to) channel allocations. In oneaspect, the controller 340 may include a memory coupled to a processor(not shown for simplicity). The memory may include a non-transitorycomputer-readable medium (e.g., one or more nonvolatile memory elements,such as EPROM, EEPROM, Flash memory, a hard drive, etc.) storinginstructions that, when executed by the processor, cause the satellite300 to perform operations including (but not limited to) those describedherein with respect to FIGS. 12-15.

An example of a transceiver for use in the UT 400 or 401 is illustratedin FIG. 4. In FIG. 4, at least one antenna 410 is provided for receivingforward link communication signals (e.g., from satellite 300), which aretransferred to an analog receiver 414, where they are down-converted,amplified, and digitized. A duplexer element 412 is often used to allowthe same antenna to serve both transmit and receive functions.Alternatively, a UT transceiver may employ separate antennas foroperating at different transmit and receive frequencies.

The digital communication signals output by the analog receiver 414 aretransferred to at least one digital data receiver 416A and at least onesearcher receiver 418. Additional digital data receivers to 416N can beused to obtain desired levels of signal diversity, depending on theacceptable level of transceiver complexity, as would be apparent to oneskilled in the relevant art.

At least one user terminal control processor 420 is coupled to digitaldata receivers 416A-416N and searcher receiver 418. The controlprocessor 420 provides, among other functions, basic signal processing,timing, power and handoff control or coordination, and selection offrequency used for signal carriers. Another basic control function thatmay be performed by the control processor 420 is the selection ormanipulation of functions to be used for processing various signalwaveforms. Signal processing by the control processor 420 can include adetermination of relative signal strength and computation of variousrelated signal parameters. Such computations of signal parameters, suchas timing and frequency, may include the use of additional or separatededicated circuitry to provide increased efficiency or speed inmeasurements or improved allocation of control processing resources.

The outputs of digital data receivers 416A-416N are coupled to digitalbaseband circuitry 422 within the user terminal. The digital basebandcircuitry 422 comprises processing and presentation elements used totransfer information to and from UE 500 as shown in FIG. 1, for example.Referring to FIG. 4, if diversity signal processing is employed, thedigital baseband circuitry 422 may comprise a diversity combiner anddecoder. Some of these elements may also operate under the control of,or in communication with, a control processor 420.

When voice or other data is prepared as an output message orcommunications signal originating with the user terminal, the digitalbaseband circuitry 422 is used to receive, store, process, and otherwiseprepare the desired data for transmission. The digital basebandcircuitry 422 provides this data to a transmit modulator 426 operatingunder the control of the control processor 420. The output of thetransmit modulator 426 is transferred to a power controller 428 whichprovides output power control to a transmit power amplifier 430 forfinal transmission of the output signal from the antenna 410 to asatellite (e.g., satellite 300).

In FIG. 4, the UT transceiver also includes a memory 432 associated withthe control processor 420. The memory 432 may include instructions forexecution by the control processor 420 as well as data for processing bythe control processor 420.

In the example illustrated in FIG. 4, the UT 400 also includes anoptional local time, frequency and/or position references 434 (e.g., aGPS receiver), which may provide local time, frequency and/or positioninformation to the control processor 420 for various applications,including, for example, time and frequency synchronization for the UT400.

Digital data receivers 416A-N and searcher receiver 418 are configuredwith signal correlation elements to demodulate and track specificsignals. Searcher receiver 418 is used to search for pilot signals, orother relatively fixed pattern strong signals, while digital datareceivers 416A-N are used to demodulate other signals associated withdetected pilot signals. However, a digital data receiver 416 can beassigned to track the pilot signal after acquisition to accuratelydetermine the ratio of signal chip energies to signal noise, and toformulate pilot signal strength. Therefore, the outputs of these unitscan be monitored to determine the energy in, or frequency of, the pilotsignal or other signals. These receivers also employ frequency trackingelements that can be monitored to provide current frequency and timinginformation to control processor 420 for signals being demodulated.

The control processor 420 may use such information to determine to whatextent the received signals are offset from the oscillator frequency,when scaled to the same frequency band, as appropriate. This and otherinformation related to frequency errors and frequency shifts can bestored in a storage or memory element 432 as desired.

The control processor 420 may also be coupled to UE interface circuitry450 to allow communications between UT 400 and one or more UEs. UEinterface circuitry 450 may be configured as desired for communicationwith various UE configurations and accordingly may include varioustransceivers and related components depending on the variouscommunication technologies employed to communicate with the various UEssupported. For example, UE interface circuitry 450 may include one ormore antennas, a wide area network (WAN) transceiver, a wireless localarea network (WLAN) transceiver, a Local Area Network (LAN) interface, aPublic Switched Telephone Network (PSTN) interface and/or other knowncommunication technologies configured to communicate with one or moreUEs in communication with UT 400.

As described above with respect to FIG. 1, the UT resource controller421 may allow the UT 400 to transmit buffered data to a gateway via asatellite using contention-based resources of the satellite system 100during a time period prior to receiving a grant for scheduled RLresources. The UT resource controller 421 may also allow the UT 400 totransmit a buffer status report on the contention-based resources duringthe time period. For some implementations, the UT resource controller421 may cause the UT 400 to terminate data transmissions on thecontention-based resources (e.g., after expiration of the time period orupon the grant of scheduled RL resources to the UT). Upon receiving thegrant of the scheduled RL resources, the UT resource controller 421 mayallow the UT 400 to transmit additional portions of the buffered data tothe gateway 200 or 201, via satellite 300, on the scheduled RL resourcesgranted by the SAN 150. In some aspects, the UT resource controller 421may be included within or associated with control processor 420, forexample, as depicted in FIG. 4. In other aspects, the UT resourcecontroller 421 may be included within or associated with any othersuitable component of the UT 400.

FIG. 5 is a block diagram illustrating an example of UE 500, which alsocan apply to UE 501 of FIG. 1. The UE 500 as shown in FIG. 5 may be amobile device, a handheld computer, a tablet, a wearable device, a smartwatch, or any type of device capable of interacting with a user, forexample. Additionally, the UE may be a network side device that providesconnectivity to various ultimate end user devices and/or to variouspublic or private networks. In the example shown in FIG. 5, the UE 500may comprise a LAN interface 502, one or more antennas 504, a wide areanetwork (WAN) transceiver 506, a wireless local area network (WLAN)transceiver 508, and a satellite positioning system (SPS) receiver 510.The SPS receiver 510 may be compatible with the Global PositioningSystem (GPS), GLONASS and/or any other global or regional satellitebased positioning system. In an alternate aspect, the UE 500 may includea WLAN transceiver 508, such as a Wi-Fi transceiver, with or without theLAN interface 502, WAN transceiver 506, and/or SPS receiver 510, forexample. Further, UE 500 may include additional transceivers such asBluetooth, ZigBee and other known technologies, with or without the LANinterface 502, WAN transceiver 506, WLAN transceiver 508 and/or SPSreceiver 510. Accordingly, the elements illustrated for UE 500 areprovided merely as an example configuration and are not intended tolimit the configuration of UEs in accordance with the various aspectsdisclosed herein.

In the example shown in FIG. 5, a processor 512 is connected to the LANinterface 502, the WAN transceiver 506, the WLAN transceiver 508 and theSPS receiver 510. Optionally, a motion sensor 514 and other sensors mayalso be coupled to the processor 512.

A memory 516 is connected to the processor 512. In one aspect, thememory 516 may include data 518 which may be transmitted to and/orreceived from the UT 400, as shown in FIG. 1. Referring to FIG. 5, thememory 516 may also include stored instructions 520 to be executed bythe processor 512 to perform the process steps for communicating withthe UT 400, for example. Furthermore, the UE 500 may also include a userinterface 522, which may include hardware and software for interfacinginputs or outputs of the processor 512 with the user through light,sound or tactile inputs or outputs, for example. In the example shown inFIG. 5, the UE 500 includes a microphone/speaker 524, a keypad 526, anda display 528 connected to the user interface 522. Alternatively, theuser's tactile input or output may be integrated with the display 528 byusing a touch-screen display, for example. Once again, the elementsillustrated in FIG. 5 are not intended to limit the configuration of theUEs disclosed herein and it will be appreciated that the elementsincluded in the UE 500 will vary based on the end use of the device andthe design choices of the system engineers.

Additionally, the UE 500 may be a user device such as a mobile device orexternal network side device in communication with but separate from theUT 400 as illustrated in FIG. 1, for example. Alternatively, the UE 500and the UT 400 may be integral parts of a single physical device.

As mentioned above, GSO satellites are deployed in geostationary orbitsat approximately 35,000 km above the Earth's surface, and revolve aroundthe Earth in an equatorial orbit at the Earth's own angular velocity. Incontrast, NGSO satellites are deployed in non-geostationary orbits andrevolve around the Earth above various paths of the Earth's surface atrelatively low altitudes (e.g., as compared with GSO satellites).

For example, FIG. 6 shows a diagram 600 depicting a first constellation610 of NGSO satellites 300A-300H and a second constellation 620 of GSOsatellites 621A-621D in orbit around Earth 630. Although depicted inFIG. 6 as including only eight NGSO satellites 300A-300H, the firstconstellation 610 may include any suitable number of NGSO satellites,for example, to provide world-wide satellite coverage. For someimplementations, the first constellation 610 may include between 600 and900 NGSO satellites. Similarly, although depicted in FIG. 6 as includingonly four GSO satellites 621A-621D, the second constellation 620 mayinclude any suitable number of GSO satellites, for example, to provideworld-wide satellite coverage. In addition, although not shown in FIG. 6for simplicity, one or more other constellations of GSO satellitesand/or one or more other constellations of NGSO satellites may be inorbit above Earth 630.

The first constellation 610, which may hereinafter be referred to as theNGSO satellite constellation 610, may provide a first satellite serviceto most, if not all, areas on Earth 630. The second constellation 620,which may hereinafter be referred to as the GSO satellite constellation620, may provide a second satellite service to large portions of Earth630. The first satellite service may be different than the secondsatellite service. For some aspects, the first satellite serviceprovided by the NGSO satellite constellation 610 may correspond to aglobal broadband Internet service, and the second satellite serviceprovided by the GSO satellite constellation 620 may correspond to asatellite-based broadcast (e.g., television) service. Further, for atleast some implementations, each of NGSO satellites 300A-300H may be oneexample of satellite 300 of FIGS. 1 and 3.

The NGSO satellites 300A-300H may orbit the Earth 630 in any suitablenumber of non-geosynchronous orbital planes (not shown for simplicity),and each of the orbital planes may include a plurality of NGSOsatellites (e.g., such as one or more of the NGSO satellites 300A-300H).The non-geosynchronous orbital planes may include, for example, polarorbital patterns and/or Walker orbital patterns. Thus, to a stationaryobserver on Earth 630, the NGSO satellites 300A-300H appear to movequickly across the sky in a plurality of different paths across theEarth's surface, with each of the NGSO satellites 300A-300H providingcoverage for a corresponding path across the earth's surface.

In contrast, the GSO satellites 621A-621D may be in a geosynchronousorbit around Earth 630 and thus, to a stationary observer on Earth 630,may appear motionless in a fixed position in the sky located above theEarth's equator 631. Each of the GSO satellites 621A-621D maintains arelatively fixed line-of-sight with a corresponding GSO ground stationon Earth 630. For example, GSO satellite 621B is depicted in FIG. 6 asmaintaining a relatively fixed line-of-sight with a GSO ground station625. It is noted that for a given point on the surface of Earth 630,there may be an arc of positions in the sky along which the GSOsatellites 621A-621D may be located. This arc of GSO satellite positionsmay be referred to herein as the GSO arc 640. The receiving area for aGSO ground station (e.g., such as GSO ground station 625) may be definedby an antenna pattern of typically fixed orientation and fixed beamwidth (such as a beam width defined by an ITU specification). Forexample, the GSO ground station 625 is depicted as transmitting a beam626 towards GSO satellite 621B.

In some aspects, each of the NGSO satellites 300A-300H may include anumber of directional antennas to provide high-speed forward links(e.g., downlinks) with user terminals such as UT 400 of FIG. 1 and/orwith gateways such as gateway 200 of FIG. 1. A high-gain directionalantenna achieves higher data rates and is less susceptible tointerference than an omni-directional antenna by focusing radiation intoa relatively narrow beam width (as compared to the relatively wide beamwidth associated with an omni-directional antenna). For example, asdepicted in FIG. 6, the coverage area 613A provided by a beam 612Atransmitted from NGSO satellite 300A is relatively small compared to thecoverage area 623A provided by a beam 622A transmitted from GSOsatellite 621A.

Because the NGSO satellites 300A-300H revolve around the earth 630relatively quickly (e.g., approximately every 90 minutes forlow-earth-orbit (LEO) satellites), their positions change quicklyrelative to a fixed location on earth 630. To provide coverage over awide area of the earth's surface (e.g., to provide Internet servicesacross the United States), each of the NGSO satellites 300A-300H mayprovide coverage for a corresponding path across the earth's surface.For example, the NGSO satellites 300A-300H may each transmit any numberof beams, and one or more of the beams may be directed towardsoverlapping regions on the earth's surface. As used herein, thefootprint of a satellite is the surface area (on Earth) within which allUTs can communicate with the satellite (above a minimum elevationangle). The area covered by a beam transmitted (e.g., from acorresponding antenna) of the satellite is referred to herein as thebeam coverage area. Thus, the footprint of a satellite may be defined bya number of beam coverage areas provided by a number of beamstransmitted from the satellite.

FIG. 7 shows a diagram 700 depicting satellite 300 transmitting a number(N) of beams 710(1)-710(N) from a respective number (N) of antennas352(1)-352(N). Referring also to FIG. 3, each of the antennas352(1)-352(N) may be coupled to a corresponding forward path (FP) in theforward transponder 310 of satellite 300. Each of the beams710(1)-710(N) may be used to transmit data from satellite 300 to one ormore user terminals (e.g., UT 400 of FIG. 4) that are located within thebeam's coverage area on Earth. Thus, in some aspects, the beams710(1)-710(N) may represent the forward service link between satellite300 and a number of UTs 400. For the example diagram 700 of FIG. 7, thebeams 710(1)-710(N) are depicted as providing coverage areas720(1)-720(N), respectively, on Earth 630. Together, the coverage areas720(1)-720(N) provided by respective beams 710(1)-710(N) may define thefootprint of satellite 300.

Each of the coverage areas 720(1)-720(N) may extend across an entirewidth of the satellite's footprint. In some implementations, thecoverage areas 720(1)-720(N) may be of other suitable shapes, sizes,and/or orientations. Further, for at least some implementations, allsatellites 300 in the NGSO satellite constellation 610 may havesubstantially similar footprints. Each of the beams 710(1)-710(N)operates as a respective communications channel of the satellite 300. Asthe satellite 300 passes over a user terminal on the surface of theearth 630, the channel quality of a given beam (e.g., as measured by theuser terminal) may deteriorate, whereas the channel quality of adifferent beam may improve. Thus, it may be necessary to periodicallyswitch the communications channel for the user terminal from one beam toanother. This process may be referred to herein as “inter-beamhandover.”

Adjacent pairs of the coverage areas 720(1)-720(N) may touch and/oroverlap each other, for example, so that the footprint provided by thebeams 710(1)-710(N) may have minimal coverage gaps. In the example ofFIG. 7, the intersection of beams 710(1) and 710(2) form an overlapregion 730. Based on the movements of the satellite 300, a user terminallying exclusively within coverage area 720(1) (e.g., and outside theoverlap region 730) at a first time may eventually fall within theoverlap region 730 at a second time. When the user terminal is withinthe overlap region 730, it may be able to communicate with satellite 300using beam 710(1) or beam 710(2). At a certain point in the satellite'sorbit, the channel quality of beam 710(2) will exceed the channelquality of beam 710(1), thus prompting an inter-beam handover from thecurrent beam 710(1) (e.g., the “source beam”) to the new beam 710(2)(e.g., the “target beam”). For example, the inter-beam handover may betriggered when the user terminal crosses a switching threshold 740(e.g., such that the user terminal is subsequently more prominentlypositioned within the coverage area 720(2) of the target beam 710(2)than the coverage area 720(1) of the source beam 710(1)).

The satellite 300 may be controlled by a network controller (e.g., SAN150 of FIG. 1) on the surface of the earth 630. More specifically, eachbeam 710(1)-710(N) may be managed and/or controlled by a respectivescheduler provided within, or otherwise associated with, the networkcontroller. During an inter-beam handover, the scheduler for the sourcebeam hands off communications with the user terminal to the schedulerfor the target beam. The network controller and the user terminal mayperform this operation synchronously, for example, based on a timelinespecified in a beam transition table.

Referring also to FIG. 1, propagation delays associated withtransmitting signals from UT 400 to SAN 150 via satellite 300 (e.g., onthe return link) may be on the order of 20 milliseconds (ms), andpropagation delays associated with transmitting signals from SAN 150 toUT 400 via satellite 300 (e.g., on the forward link) may be on the orderof 20 ms. Thus, for one example implementation of satellite system 100,the round trip time (RTT) of a signal exchange between UT 400 and SAN150 via satellite 300 may be approximately 40 ms. In addition, the UT400 and SAN 150 may have combined processing delays (e.g., turn-aroundtimes) of approximately 6 ms, and the scheduler within or associatedwith SAN 150 may also have processing delays of a few milliseconds.Thus, there may be a delay of approximately 47 ms (or more) between thetime that the UT 400 transmits a signal to SAN 150 via satellite 300 andthe time that the UT 400 receives a response from the SAN 150 viasatellite 300. This delay may hereinafter be referred to as an “RTTdelay.”

When the UT 400 receives data for transmission to gateway 200 (e.g.,from one or more UEs 500 associated with UT 400), the UT 400 may storethe data in a transmit buffer until return link resources are availablefor transmitting the data to gateway 200 via satellite 300. In someaspects, when data is stored in the transmit buffer of UT 400, ascheduling request (SR) and/or a buffer status report (BSR) may betriggered. The UT 400 may transmit scheduling requests during SRopportunities, which may occur at regular intervals. For example, forimplementations in which SR opportunities occur every 40 ms, the UT 400may be delayed in transmitting the scheduling request by as much as 40ms after the scheduling request is triggered. This delay may hereinafterbe referred to as an “SR opportunity delay.” When the next SRopportunity occurs, the UT 400 may transmit a scheduling request to theSAN 150. In response thereto, the SAN 150 may grant dynamicallyscheduled return link resources to the UT 400, for example, bytransmitting a scheduling grant to the UT 400. Upon receipt of thescheduling grant, the UT 400 may transmit the buffered data using thereturn link resources granted by the SAN 150.

For example, FIG. 8A shows a timing diagram depicting an exampleoperation 800A for transmitting data from a UT to a network controllervia a satellite using return link resources granted by the networkcontroller. For purposes of discussion herein, the network controllermay correspond to SAN 150 of FIG. 1, and the user terminal (UT) maycorrespond to UT 400 of FIG. 4. At time t₀, data (e.g., a number of newpackets) arrives at the UT. The data, which may be received from anumber of UEs 500 associated with the UT, may be stored in a transmitbuffer of the UT. In some aspects, storing the data in the transmitbuffer of the UT may trigger a scheduling request and/or a BSR at timet₁. For the example of FIG. 8A, the next SR opportunity is not untiltime t₂, and thus the UT may not transmit a scheduling request to theSAN until time t₂. The time period between times t₁ and t₂ is denoted inFIG. 8A as the SR opportunity delay.

At time t₂, a SR opportunity occurs, and the UT transmits a schedulingrequest to the SAN. The scheduling request may be used by the UT torequest a grant of dynamically scheduled return link resources of thesatellite system 100. As mentioned above, this may occur when the UT hasbuffered data ready for transmission but does not have a resource grantfor use of a physical return-link shared channel (PRSCH) of thesatellite system 100. In some aspects, the scheduling request may betransmitted on a physical return-link control channel (PRCCH) of thesatellite system 100.

At time t₃, the SAN receives the scheduling request, and after aprocessing delay, transmits a grant for return link resources (RL grant)to the UT at time t₄. The UT receives the RL grant at time t₅, and aftera processing delay, begins transmitting the buffered data to the SAN viasatellite 300 on the granted resources of the PRSCH at time t₆.

The SAN may receive the transmitted data at time t₇, and after aprocessing delay, may transmit either an acknowledgement (ACK) or anegative acknowledgement (NACK) to the UT at time t₈. An ACK mayindicate that the SAN received and decoded the transmitted data, while aNACK may indicate that the SAN did not receive or decode all of thetransmitted data. The UT may receive the ACK/NACK at time t₉.

As depicted in the example of FIG. 8A, the total delay between the timethat the UT receives the transmit data (time t₀) and the time that theUT transmits the data to the SAN on the granted return link resources(time t₆) may be the sum of the SR opportunity delay and the RTT delay.For implementations in which the maximum SR opportunity delay isapproximately 40 ms and the RTT delay is approximately 47 ms, the totalUT transmission delay may be approximately 97 ms (or more).

Because humans may perceive propagation delays of approximately 100 ms,UT transmission delays of approximately 97 ms (or more) may result inunacceptable user experience, for example, when the transmit data isreal-time data such as voice or video data. Thus, there is a need toreduce the UT transmission delays associated with satellite system 100.

As described in more detail below, the example implementations mayreduce UT transmission delays by allowing a UT to transmit buffered dataon contention-based resources of satellite system 100 while the UT waitsfor a scheduled grant of return link resources (e.g., PRSCH resources)from the SAN. In this manner, the UT may begin to transmit buffered datato the SAN via satellite 300 prior to receiving a RL grant from the SAN,which in turn may significantly reduce the UT transmission delaysdescribed above with respect to FIG. 8A (and thereby improve userexperience).

FIG. 8B shows a timing diagram depicting an example operation 800B fortransmitting data from a UT to a network controller in accordance withexample implementations. For purposes of discussion herein, the networkcontroller may correspond to SAN 150 of FIG. 1, and the user terminal(UT) may correspond to UT 400 of FIG. 4. At time t₀, data (e.g., anumber of new packets) arrives at the UT. The data, which may bereceived from a number of UEs 500 associated with the UT, may be storedin a transmit buffer of the UT. In some aspects, storing the data in thetransmit buffer of the UT may trigger the generation of a buffer statusreport (BSR) and/or may trigger the generation of a scheduling request(SR). For the example of FIG. 8B, the next SR opportunity is not untiltime t₄, and thus the UT may not transmit a scheduling request on thePRCCH to the SAN until time t₄ (although for other implementations, theSR opportunity may occur at times other than as depicted in FIG. 8B).

In accordance with example implementations, the SAN may allocatecontention-based resources to the UT, for example, so that the UT maybegin transmitting return link data on the contention-based resources tothe SAN via the satellite 300 prior to receiving a grant for scheduledreturn link resources of the satellite system. For some implementations,a radio controller circuit (RRC) included within or associated with theSAN may allocate the number and/or size of resource blocks available tothe UT as part of the contention-based resources, and may select themodulation and coding scheme (MCS) to be used by the UT whentransmitting data on the contention-based resources. In some aspects,the SAN may activate the contention-based resources allocated to the UTby transmitting a grant of the contention-based resources to the UTusing a physical-forward link control channel (PFCCH). The PFCCH may beindependent of the contention-based resources (e.g., the PFCCH mayinclude resource blocks different in time, frequency, and/or size thanresource blocks associated with the contention-based resources). In someaspects, the PFCCH grant may identify the size and location of allocatedresource block(s) of the contention-based resources, the MCS of theallocated resource block(s) of the contention-based resources, and/or atime period during which the UT may use the contention-based resourcesfor RL data transmissions. In other aspects, signals transmitted on thePFCCH may also indicate the availability of a dedicated physical returnlink control channel (PRCCH), for example, upon which the UT mayperiodically transmit control information to the SAN via satellite 300using resource blocks independent of the resource blocks associated withthe contention-based resources.

Thus, for at least some implementations disclosed herein, the SAN mayconfigure the contention-based resources for each UT in the terrestrialportion of the satellite system. For one example, the SAN may allocateone or more specific resource blocks to each UT (or to each group ofUTs) and/or may indicate a number of time intervals during which the UT(or group of UTs) may use the allocated resource blocks of thecontention-based resources. For another example, when the resourceblocks associated with the contention-based resources are shared betweena number (N) of groups of UTs, each group of UTs may share every N^(th)subframe of the contention-based resources for data transmissions to theSAN via the satellite. In some aspects, the SAN may indicate thesub-frames upon which the UT (or group of UTs) may transmit data usingthe contention-based resources.

For some implementations, once the contention-based resources allocatedto the UT have been activated by the SAN (e.g., based on an activationsignal transmitted to the UT on the PFCCH), the UT may begintransmitting data on the allocated resource block(s) of thecontention-based resources based on an “on-trigger.” For example, ifdata queued in the UT triggers generation of a buffer status report(BSR) and the UT has not received a grant for scheduled return linkresources of the satellite system, then the UT may begin transmittingthe queued data using the allocated resource block(s) of thecontention-based resources. Thus, in some aspects, triggering thegeneration of the BSR may operate as the “on-trigger” forcontention-based resources allocated to the UT and activated by the SAN.Conversely, if scheduled RL resources are available to the UT when theBSR is triggered (e.g., the UT has received a grant for PRSCHresources), then the UT may transmit buffered data using the scheduledRL resources. In this case, the BSR may not operate as the on-triggerfor the contention-based resources.

Thus, in contrast to the example operation 800A of FIG. 8A, the exampleoperation 800B of FIG. 8B may allow the UT to begin transmitting data tothe SAN via satellite 300 on the contention-based resources withoutreceiving an explicit grant message, from the SAN, that grants scheduledreturn link resources to the UT. In addition, the UT may transmit theBSR to the SAN using the contention-based resources, for example, asdepicted in FIG. 8B. In some aspects, the SAN may allocate one or morefirst resource blocks of the contention-based resources to the UT (or toa group of UTs that includes the UT of FIG. 8B) for transmittingbuffered data to the SAN via the satellite, and may allocate one or moresecond resource blocks of the contention-based resources to another UT(or to another group of UTs) for transmitting the BSR to the SAN via thesatellite. The one or more first resource blocks of the contention-basedresources may be orthogonal to the one or more second resource blocks ofthe contention-based resources, for example, so that one group of UTsmay transmit data using the first resource blocks of thecontention-based resources while another group of UTs concurrentlytransmits data using the second resource blocks of the contention-basedresources.

As shown in FIG. 8B, the SAN may activate the contention-based resourcesby transmitting a grant on the PFCCH prior to time t₀. As discussedabove, the PFCCH grant may configure the size, location, and MCS ofresource blocks allocated to the UT, and may indicate a number oftransmit occasions or opportunities during which the UT may transmit RLdata on the contention-based resources. For the example of FIG. 8B, thePFCCH grant allocates every fourth subframe to the UT for transmittingRL data to the satellite (e.g., subframe n, subframe n+4, subframe n+8,subframe n+12, and subframe n+16). For other implementations, the PFCCHgrant may allocate different numbers of subframes to the UT and/orconfigure different intervals between the subframes allocated to the UT(e.g., by allocating every eight subframe to the UT, by allocating everytenth subframe to the UT, and so on). In some aspects, the SAN mayrelease or de-activate the contention-based resources by transmitting arelease signal to the UT on the PFCCH (not shown for simplicity).

As mentioned above, the arrival of new data packets at the UT maytrigger the generation of the BSR. For the example of FIG. 8B, the BSRmay be triggered for transmission to the satellite at time t₁, whichcorresponds to the first subframe (subframe n) allocated to the UT.Specifically, at time t₁, the UT may begin transmitting a first portionof the buffered data (e.g., a first subset of the first portion of thebuffered data) and the BSR to the SAN via satellite 300 on subframe n ofthe contention-based resources of the satellite system 100. In someaspects, the UT may start the contention-based resource timer based onthe first subframe of the contention-based resources allocated to the UTfor RL data transmissions at time t₁, as depicted in the example of FIG.8B. In other aspects, the UT may start the contention-based resourcetimer in response to the triggering or the generation of the BSR (e.g.,just after time t₀). The contention-based resource timer may be used todefine a time period 820 during which the UT may transmit RL data on thecontention-based resources of the satellite system.

At time t₂, the SAN may receive the RL data and the BSR in subframe ntransmitted from the UT. In some aspects, reception of the RL dataand/or the BSR may operate as an implicit scheduling request (SR)informing the SAN that the UT has buffered data for transmission to theSAN. In this manner, the UT may not need to transmit a separate SR tothe SAN. In response to the implicit SR, the SAN may schedule a grant ofRL resources of the satellite system to the UT.

The UT may continue transmitting subsets of the first portion of thebuffered data to the SAN during subsequent transmit opportunitiesindicated by the PFCCH grant. More specifically, for the exampledepicted in FIG. 8B, the UT may transmit a second subset of the firstdata portion in a second subframe (subframe n+4) at time t₂, maytransmit a third subset of the first data portion in a third subframe(subframe n+8) at time t₃, may transmit a fourth subset of the firstdata portion in a fourth subframe (subframe n+12) at time t₄, and maytransmit a fifth subset of the first data portion in a fifth subframe(subframe n+16) at time t₅. This process may continue until either thecontention-based resource timer expires or the UT receives a grant ofscheduled return link resources from the SAN (e.g., where the UT maytransmit an m^(th) subset of the first data portion in an m^(th)subframe at time t_(am), where “m” is an integer greater than or equalto 1).

The SAN may receive the second subset of the first data portion insubframe n+4 at time t₃, may receive the third subset of the first dataportion in subframe n+8 at time t₄, may receive the fourth subset of thefirst data portion in subframe n+12 at time t₅, and may receive thefifth subset of the first data portion in subframe n+16 at time t₆. Asdepicted in FIG. 8B, the RL data transmitted by the UT in subframe n,subframe n+4, subframe n+8, and subframe n+12 is properly received bythe SAN. However, the RL data transmitted by the UT in subframe n+16 isreceived in error by the SAN, for example, due to collisions on thecontention-based resources. In response thereto, the SAN may identifywhich of the UTs transmitted the RL data in subframe n+16, and mayinstruct the identified UT to re-transmit the RL data, as described inmore detail below.

Although not shown in FIG. 8B for simplicity, the UT may transmit the SRto the SAN during the time period 820 using the PRCCH (or anotherdedicated channel) of the scheduled RL resources. For someimplementations, the dedicated resources (e.g., the PRCCH) upon whichthe SR and other control information may be transmitted by the UT mayoccur with a periodicity selected, for example, by the SAN. Thededicated resources may be scheduled to occur during selected intervalsof the time period 820, while all other (e.g., non-selected) intervalsof the time period 820 may be used for data transmissions on thecontention-based resources. In some aspects, the PRCCH may be allocatedto (or scheduled for) the UT between selected pairs of subframes of thecontention-based resources. For some implementations, UT transmissionson the contention-based resources may be paused or suspended duringselected intervals for which dedicated RL resources are granted to theUT (e.g., to transmit control information to the SAN).

For some implementations, the contention-based resources may besemi-statically configured by the SAN and allocated to a group of UTsfor an adjustable period of time. In contrast to the dynamicallyscheduled RL grants depicted in FIG. 8A, use of the contention-basedresources may avoid the need for specific RL grant messages over thePFCCH of the satellite system 100 for each subframe, thereby not onlyreducing overhead on the PFCCH but also allowing the UT more immediateaccess to return link resources of satellite system 100. It is notedthat the scheduling request and grant messages associated withdynamically scheduled resources (e.g., as described above with respectto FIG. 8A) are not needed to activate the contention-based resourcesupon which the UT may transmit buffered data. Instead, thecontention-based resources may be activated by a single grant (e.g., onthe PFCCH) by the SAN, as described above.

At time t₇, which for the example of FIG. 8B occurs after the SRopportunity, the SAN transmits a RL grant to the UT. In some aspects,the amount of RL resources granted by the SAN may be based on the BSRpreviously received from the UT on the contention-based resources. Inother aspects, the amount of RL resources granted by the SAN via the RLgrant may be based, at least in part, on the amount of data receivedfrom the UT on the contention-based resources. In this manner, theallocation of scheduled RL resources may be selectively adjusted by theSAN to account for data transmissions during time period 820 on thecontention-based resources. The UT receives the RL grant at time t₈, andafter a processing delay indicated by arrow 830, may begin transmittinga second portion (e.g., a remaining portion) of the buffered data to theSAN (via satellite 300) on the granted RL resources (e.g., on the PRSCH)at time t₉. For the example of FIG. 8B, the RL grant may include arequest to re-transmit, using the scheduled RL resources, the datareceived in error by the SAN at time t₆.

In some implementations, reception of the RL grant by the UT mayde-activate, suspend, or terminate the allocation of contention-basedresources to the UT, regardless of whether the time period 820 hasexpired. More specifically, the UT may, upon receiving the RL grant attime t₈, prevent additional data transmissions on the contention-basedresources until a next BSR is triggered (e.g., in response to newpackets arriving at the UT). Thus, in at least some implementations,allocation of the contention-based resources to the UT may be suspendedor terminated when the UT receives a grant for scheduled RL resources ofthe satellite system. In this manner, reception of the RL grant by theUT may operate as an “off-trigger” that suspends or terminates theallocation of contention-based resources to the UT.

The SAN may receive the RL data transmitted by the UT on the PRSCH attime t₁₀. Although not shown in FIG. 8B for simplicity, the SAN maytransmit an ACK to the UT on the PFCCH to acknowledge reception of thereceived RL data.

As mentioned above, the resource blocks of the contention-basedresources may differ in time, frequency, and size from the resourceblocks of the scheduled RL resources. For some implementations, theresource blocks associated with the contention-based resources may beorthogonal to the resource blocks of the scheduled RL resources.

Although depicted in FIG. 8B as lasting until reception of the RL grantby the UT at time t₈, the allocation of contention-based resources tothe UT may be configurable (and/or dynamically adjusted) by the SANbased, for example, on the amount of loading on the satellite system'sresources. For example, for at least one other implementation, the UTmay be allocated only enough contention-based resources to transmit theBSR to the SAN.

In other implementations, the UT may terminate the transmission of dataon the contention-based resources after expiration of the time period820. For example, FIG. 8C shows a timing diagram depicting anotherexample operation 800C for transmitting data from the UT to the SAN inaccordance with example implementations.

The example operation 800C of FIG. 8C is similar to the exampleoperation 800B of FIG. 8B except for the conditions upon which thecontention-based resources allocated to the UT may be suspended orterminated. More specifically, for the example operation 800C, the UTmay start the contention-based resources timer to commence the timeperiod 820 at time t₁. For other implementations, the UT may commencethe time period 820 in response to the triggering or the generation ofthe BSR, for example, just after time t₀. During the time period 820,the UT may transmit RL data using allocated subframes of thecontention-based resources in the manner described above with respect toFIG. 8B. Upon expiration of the time period 820 at time t₅, which mayindicate suspension of the contention-based resources allocated by theSAN, the UT may terminate data transmissions on the contention-basedresources of satellite system 100. In this manner, the UT may preventadditional data transmissions on the contention-based resources afterexpiration of the time period 820 at time t₅ (denoted in FIG. 8C asEOTP). Thus, in some aspects, expiration of the time period 820 (e.g.,as indicated by the contention-based resource timer reaching a zerovalue) may operate as an “off-trigger” that suspends or terminates theallocation of contention-based resources to the UT.

As mentioned above, the UT may include a contention-based resource timerthat determines when the time period 820 expires. In some aspects, theinitial value of the contention-based resource timer (and thus theduration of the time period 820) may be configured by a radio resourcecontrol (RRC) associated with the SAN. For at least someimplementations, there may be no implicit release of the sharedcontention-based resources (e.g., the contention-based resources may notbe reclaimed by the SAN if a corresponding group of UTs does nottransmit data thereon for a given time period). Instead, the sharedcontention-based resources may be available to the corresponding groupof UTs for each duration of the time period 820. The RRC may select aduration of the time period 820 that achieves an optimal balance betweenthe duration of the time period 820 and the likelihood of collisions onthe shared contention-based resources. For example, while increasing thetime period 820 may reduce UT transmission delays, it may increase thelikelihood of collisions on the shared contention-based resources.Conversely, while decreasing the time period 820 may decrease thelikelihood of collisions, it may increase UT transmission delays. Insome aspects, the RRC may select a value for the time period 820 thatcorresponds to the time period within which the UT may expect to receivea grant of return link resources. For one example, the RRC may select avalue of 40 ms for the time period 820 (although other time values maybe used).

The RRC may configure the contention-based resources in both time andfrequency. More specifically, in the frequency domain, the RRC mayallocate various numbers of resource blocks to a given group of UTs. Forexample, in some operating environments, the RRC may allocate arelatively small number of resource blocks (e.g., 2 resource blocks) toa group of UTs, and in other operating environments, the RRC mayallocate a relatively large number of resource blocks (e.g., 50 resourceblocks) to the group of UTs. In the time domain, the RRC may allocatevarious numbers of subframes to the group of UTs for data transmissions.For example, in some operating environments, the RRC may allocate everyother subframe to the group of UTs for data transmissions, and in otheroperating environments, the RRC may allocate every third subframe (orevery fifth subframe, every tenth subframe, and so on) to the group ofUTs for data transmissions.

As mentioned above, the contention-based resources of satellite system100 may be shared by a group of UTs. In some implementations, the SANmay assign, to each UT within a given group of UTs, a uniquedemodulation reference signal (DM-RS) shift to be applied on transmittedreference symbols. Thereafter, each UT within the group of UTs maytransmit data on the contention-based resources using its assigned DM-RSshift value. In some aspects, 12 unique DM-RS shifts may be available,thereby allowing the SAN to distinguish transmissions from up to 12different UTs.

If there is a collision on the contention-based resources (e.g., if morethan one UT transmits data on the contention-based resources at the sametime), the SAN may be able to identify which of the UTs attempted totransmit data based on the DM-RS shifts associated with the receivedsignals. More specifically, because the unique DM-RS shifts assigned tothe group of UTs are orthogonal to one another, the SAN may identifywhich UTs attempted to transmit data by decoding the DM-RS shifts. Thus,although data transmitted from the identified UTs may be lost due tocollisions, the SAN may request data retransmissions from the identifiedUTs, for example, using a hybrid automatic repeat request (HARQ)operation. HARQ is a method by which a receiving device (e.g., the SAN)may request retransmission of data that was received in error (e.g.,from the UTs identified by DM-RS shifts). More specifically, HARQ allowsfor buffering and combining of incorrectly received data (e.g., packets,frames, PDUs, MPDUs, etc.) to potentially reduce the number ofretransmissions needed to properly reconstruct a particular unit ofdata. For some implementations, the SAN may immediately transmit RLgrants to the UTs identified in the collisions, for example, as depictedin the example of FIG. 8B.

As mentioned above, the RRC may select the duration of the time period820. More specifically, the RRC may define a periodicity of theallocated contention-based resources. In some aspects, each allocationof contention-based resources may include between approximately 10 and640 subframes. In some implementations, the SAN may activate or allocatethe contention-based resources by transmitting a signal to acorresponding group of UTs on the PFCCH associated with a givensatellite 300. In some aspects, the signal may also indicate whether theRL grant is semi-persistent or dynamic. In other aspects, the RL grantmay include a special field to carry the contention-based resourcesactivation signal, which in turn may be scrambled by a contention-basedradio network temporary identifier (C-RNTI).

FIG. 9 is a block diagram of a user terminal (UT) 900 in accordance withexample implementations. The UT 900, which may be one implementation ofthe UT 400 of FIG. 1, may include at least an antenna 910, a duplexer912, a transceiver 915, a processor 920, and a memory 932. The duplexer912, which may correspond to duplexer 412 of FIG. 4, may selectivelyroute signals received from one or more satellites via antenna 910 totransceiver 915, and may selectively route signals from transceiver 915to antenna 910 for transmission to one or more satellites. In someaspects, antenna 910 may be a directional antenna. Further, although UT900 is shown in FIG. 9 as including only one antenna 910, for otherimplementations, UT 900 may include any suitable number of antennas.

The transceiver 915, which may correspond to the analog receiver 414,digital receivers 416A-416N, transmit modulator 426, and/or analogtransmit power 430 of FIG. 4, may be coupled to antenna 910 via duplexer912. More specifically, the transceiver 915 may be used to transmitsignals to and receive signals from a number of satellites 300. Althoughnot shown in FIG. 9 for simplicity, the transceiver 915 may include anysuitable number of transmit chains and/or may include any suitablenumber of receive chains.

The processor 920, which may be one implementation of the controlprocessor 420 of FIG. 4, is coupled to transceiver 915 and to memory932. The processor 920 may be any suitable one or more processorscapable of executing scripts or instructions of one or more softwareprograms stored in the UT 900 (e.g., within memory 932).

The memory 932, which may be one implementation of memory 432 of FIG. 4,may include data buffers 932A to store data (e.g., received from one ormore associated UEs 500) for transmission to the SAN via one or moresatellites 300.

The memory 932 may include a timer 932B that determines when the UT 900is to terminate data transmissions on the contention-based resources ofthe satellite system 100. As described above with respect to FIG. 8C,the timer 932B may be set to an initial value that corresponds to thetime period 820 selected by the RRC, and may be commenced in response toa triggering of the scheduling request.

The memory 932 may include a transmission (TX) parameters table 932Cthat stores a number of parameters associated with the allocation ofshared contention-based resources to the UT 900. For example, the TXparameters table 932C may store a DM-RS shift assigned by the SAN, maystore an indication of the time and/or frequency allocations of thecontention-based resources (e.g., which resource blocks and/or whichsubframes may be used by UT 900), and may store other informationpertaining to the allocation of contention-based resources to UT 900.

The memory 932 may include a non-transitory computer-readable storagemedium (e.g., one or more nonvolatile memory elements, such as EPROM,EEPROM, Flash memory, a hard drive, and so on) that may store thefollowing software modules (SW):

-   -   a scheduling request SW module 932D to facilitate the triggering        and/or transmission of a request for scheduled return link        resources of satellite system 100, for example, as described for        one or more operations of FIGS. 11A-11C and 12A-12C;    -   a return link transmit SW module 932E to facilitate the        transmission of data to the SAN based on dynamically scheduled        grants of return link resources received from the SAN, for        example, as described for one or more operations of FIGS.        11A-11C and 12A-12C;    -   a contention-based resource transmit SW module 932F to        facilitate the transmission of data to the SAN using        contention-based resources of satellite system 100, for example,        as described for one or more operations of FIGS. 11A-11C and        12A-12C; and    -   a contention-based resource termination SW module 932G to        terminate data transmissions on the contention-based resources        of satellite system 100, for example, as described for one or        more operations of FIGS. 11A-11C and 12A-12C.

Each software module includes instructions that, when executed byprocessor 920, cause the UT 900 to perform the corresponding functions.The non-transitory computer-readable medium of memory 932 thus includesinstructions for performing all or a portion of the operations of FIGS.11A-11C and 12A-12C.

For example, processor 920 may execute the scheduling request SW module932D to facilitate the triggering and/or transmission of a request forscheduled return link resources of satellite system 100. Processor 920may execute the return link transmit SW module 932E to facilitate thetransmission of data to the SAN based on dynamically scheduled grants ofreturn link resources received from the SAN. Processor 920 may executethe contention-based resource transmit SW module 932F to facilitate thetransmission of data to the SAN using contention-based resources ofsatellite system 100. Processor 920 may execute the contention-basedresource termination SW module 932G to terminate data transmissions onthe contention-based resources of satellite system 100.

FIG. 10 shows a block diagram of an example network controller 1000 inaccordance with example implementations. The network controller 1000,which may be one implementation of the SAN 150 of FIG. 1, may include atleast an antenna (not shown for simplicity), a transceiver 1015, aprocessor 1020, a memory 1030, a scheduler 1040, and a radio resourcecontrol (RRC) 1050. The transceiver 1015 may be used to transmit signalsto and receive signals from a number of UTs 400 via one or moresatellites 300. Although not shown in FIG. 10 for simplicity, thetransceiver 1015 may include any suitable number of transmit chainsand/or may include any suitable number of receive chains.

The scheduler 1040 may dynamically schedule return link resources for anumber of UTs, for example, by transmitting RL grant messages to theUTs. The scheduler 1040 may also schedule and/or otherwise allocateshared contention-based resources to a group of UTs. The scheduler 1040may select the DM-RS shifts to be assigned to each UT in a correspondinggroup of UTs. The scheduler 1040 may schedule dynamic grants of returnlink resources, may select the size of the granted return link resources(e.g., based on received BSRs), and/or may schedule the allocation ofcontention-based resources to a group of UTs.

The RRC 1050 may configure the contention-based resources in both timeand frequency. As described above, the RRC 1050 may allocate variousnumbers of resource blocks to a given group of UTs for datatransmissions, and/or may allocate various numbers of subframes to thegroup of UTs for data transmissions. The RRC 1050 may also select theduration of the time period 820, for example, as described above withrespect to FIG. 8C.

The processor 1020 is coupled to transceiver 1015, to memory 1030, toscheduler 1040, and to RRC 1050. The processor 1020 may be any suitableone or more processors capable of executing scripts or instructions ofone or more software programs stored in the network controller 1000(e.g., within memory 1030).

The memory 1030 may include a UT profile data store 1030A to storeprofile information for a plurality of UTs. The profile information fora particular UT may include, for example, the DM-RS shift assigned tothe UT, transmission history of the UT, location information of the UT,and any other suitable information describing or pertaining to theoperation of the UT.

The memory 1030 may include a non-transitory computer-readable storagemedium (e.g., one or more nonvolatile memory elements, such as EPROM,EEPROM, Flash memory, a hard drive, and so on) that may store thefollowing software modules (SW):

-   -   a return link resource scheduling SW module 1030B to facilitate        the dynamic scheduling of return link resources for one or more        UTs, for example, as described for one or more operations of        FIGS. 11A-11C and 12A-12C; and    -   a contention-based resource allocation SW module 1030C to        facilitate the allocation of shared contention-based resources        of satellite system 100 to a group of UTs, for example, as        described for one or more operations of FIGS. 11A-11C and        12A-12C.

Each software module includes instructions that, when executed byprocessor 1020, cause the network controller 1000 to perform thecorresponding functions. The non-transitory computer-readable medium ofmemory 1030 thus includes instructions for performing all or a portionof the operations of FIGS. 11A-11C and 12A-12C.

For example, processor 1020 may execute the return link resourcescheduling SW module 1030B to facilitate the dynamic scheduling ofreturn link resources for one or more UTs. Processor 1020 may executethe contention-based resource allocation SW module 1030C to facilitatethe allocation of shared contention-based resources of satellite system100 to a group of UTs.

FIG. 11A shows an illustrative flowchart depicting an example operation1100 for transmitting data from a UT to a network controller via asatellite in accordance with example implementations. The exampleoperation 1100 may be performed by the UT 900 depicted in FIG. 9.However, it is to be understood that operation 1100 may be performed byother suitable devices capable of transmitting data to a networkcontroller via one or more satellites (e.g., satellites 300 of FIG. 1).

First, the UT 900 may receive data for transmission to a gateway via asatellite (1101). In some aspects, reception of the data may cause theUT 900 to trigger or generate a buffer status report (BSR) indicating anamount of queued return link data stored in the UT 900 (1101A). The UT900 may receive an activation signal that activates contention-basedresources allocated to the UT 900 by the SAN (1102). As described abovewith respect to FIG. 10, the RRC 1050 may configure the contention-basedresources allocated to the UT 900, and the SAN may transmit theactivation signal to the UT 900 on the PFCCH. If scheduled RL resourcesare available to the UT 900 when the BSR is triggered (e.g., the UT hasreceived a grant for PRSCH resources), then the UT 900 may transmit thebuffered data on the scheduled RL resources.

Conversely, if scheduled RL resources are not available to the UT 900(e.g., the PRSCH is not available to the UT 900 for RL datatransmissions), then the triggering or generation of the BSR may operateas the on-trigger and cause the UT 900 to commence the time period, forexample, by starting the timer 932B of FIG. 9 (1103). As described abovewith respect to FIGS. 8B-8C, in some aspects, the time period may becommenced in response to the first subframe of the activatedcontention-based resources becoming available to the UT 900 for RL datatransmissions. In other aspects, the time period may be commenced inresponse to triggering or generation of the BSR.

Assuming that the contention-based resources allocated to the UT 900have been activated by the SAN, then the UT 900 may transmit the BSR onthe activated contention-based resources (1104). The UT 900 may transmita first portion of the data on contention-based resources of thesatellite system prior to receiving a grant for scheduled return linkresources of the satellite system (1106).

The UT 900 may subsequently receive a scheduling grant for the returnlink resources (1108). In response thereto, the UT 900 may transmit asecond portion of the data on the granted return link resources (1110).

The UT 900 may terminate the transmission of data on thecontention-based resources (1112). In some aspects, the UT 900 mayterminate the contention-based resources based on receiving thescheduling grant (1112A). In other aspects, the UT 900 may terminate thecontention-based resources based on an expiration of the time periodassociated with the contention-based resource timer (e.g., the timer932B of FIG. 9) (1112B).

FIG. 11B shows an illustrative flowchart depicting an example operation1120 for transmitting data from a UT to a network controller via asatellite in accordance with example implementations. The exampleoperation 1120 may be performed by the UT 900 depicted in FIG. 9.However, it is to be understood that operation 1120 may be performed byother suitable devices capable of transmitting data to a networkcontroller via one or more satellites (e.g., satellites 300 of FIG. 1).

First, the UT 900 may receive data for transmission to a gateway via asatellite (1121). In some aspects, reception of the data may cause theUT 900 to trigger generation of a buffer status report (BSR) indicatingan amount of queued return link data stored in the UT (1121A). The UT900 may receive an activation signal that activates contention-basedresources allocated to the UT 900 by the SAN (1122). As described abovewith respect to FIG. 10, the RRC 1050 may configure the contention-basedresources allocated to the UT 900, and the SAN may transmit theactivation signal to the UT 900 on the PFCCH. If scheduled RL resourcesare available to the UT 900 when the BSR is triggered (e.g., the UT 900has received a grant for PRSCH resources), then the UT 900 may begintransmit the buffered data on the scheduled RL resources.

Conversely, if scheduled RL resources are not available to the UT 900(e.g., the PRSCH is not available to the UT 900 for RL datatransmissions), then the triggering or the generation of the BSR mayoperate as the on-trigger and cause the UT 900 to commence the timeperiod, for example, by starting the timer 932B of FIG. 9 (1123). Asdescribed above with respect to FIGS. 8B-8C, in some aspects, the timeperiod may be commenced in response to the first subframe of theactivated contention-based resources becoming available to the UT 900for RL data transmissions. In other aspects, the time period may becommenced in response to triggering or generation of the BSR.

Assuming that the contention-based resources allocated to the UT 900have been activated by the SAN, then the UT 900 may transmit, during thetime period, a first portion of the data on a plurality of subframes ofthe contention-based resources of the satellite system prior toreceiving a grant of scheduled return link resources (1124). The UT 900may transmit, during the time period on a dedicated physical return linkcontrol channel (PRCCH), a scheduling request for the grant of scheduledreturn link resources (1126). The UT 900 may terminate datatransmissions on the contention-based resources after an expiration ofthe time period irrespective of collisions on the contention-basedresources (1128).

The UT 900 may subsequently receive a grant for the scheduled RLresources (1130). In response thereto, the UT 900 may transmit a secondportion of the data on the scheduled return link resources (1132). Insome aspects, the UT 900 may receive the grant for the scheduled returnlink resources prior to the expiration of the time period, and maytransmit a second portion of the data on the scheduled return linkresources during the time period. The UT 900 may terminate datatransmissions on the contention-based resources in response to receivingthe grant for the scheduled RL resources. In other aspects, the UT 900may receive the grant for the scheduled RL resources after theexpiration of the time period, and may transmit a second portion of thedata on the scheduled RL resources after the expiration of the timeperiod. The UT 900 may prevent additional data transmissions on thecontention-based resources until a subsequent scheduling request istriggered (e.g., in response to receiving additional data fortransmission to the gateway via the satellite).

FIG. 11C shows an illustrative flowchart depicting an example operation1140 for transmitting data from a UT to a network controller via asatellite in accordance with example implementations. The exampleoperation 1140 may be performed by the UT 900 depicted in FIG. 9.However, it is to be understood that operation 1140 may be performed byother suitable devices capable of transmitting data to a networkcontroller via one or more satellites (e.g., satellites 300 of FIG. 1).

First, the UT 900 may receive data for transmission to a gateway via asatellite (1141). In some aspects, reception of the data may cause theUT 900 to trigger generation of a buffer status report (BSR) indicatingan amount of queued return link data stored in the UT 900. The UT 900may receive an activation signal that activates contention-basedresources allocated to the UT 900 by the SAN (1142). As described abovewith respect to FIG. 10, the RRC 1050 may configure the contention-basedresources allocated to the UT 900, and the SAN may transmit theactivation signal to the UT 900 on the PFCCH. If scheduled RL resourcesare available to the UT 900 when the BSR is triggered (e.g., the UT 900has received a grant for PRSCH resources), then the UT may transmit thebuffered data on the scheduled RL resources, and generation of the BSRmay not operate as the on-trigger for the contention-based resources.

Conversely, if scheduled RL resources are not available to the UT 900when the BSR is triggered (e.g., the UT 900 has not received a grant forPRSCH resources), then triggering of the BSR may operate as theon-trigger and cause the UT 900 to commence the time period, forexample, by starting the timer 932B of FIG. 9 (1143). As described abovewith respect to FIGS. 8B-8C, in some aspects, the time period may becommenced in response to the first subframe of the activatedcontention-based resources becoming available to the UT 900 for RL datatransmissions. In other aspects, the time period may be commenced inresponse to triggering or generation of the BSR.

The UT 900 may transmit, during a time period, a first portion of thedata on a plurality of subframes of the contention-based resources ofthe satellite system prior to receiving a grant of scheduled return linkresources (1144). The UT 900 may receive, from the gateway, anindication of a collision on the contention-based resources (1146). TheUT may terminate data transmissions on the contention-based resourcesafter an expiration of the time period irrespective of collisions on thecontention-based resources (1148).

The UT 900 may subsequently receive a grant for the scheduled returnlink resources (1150). In response thereto, the UT 900 may re-transmitdata associated with the indicated collision on the scheduled returnlink resources after the expiration of the time period (1152).Thereafter, the UT may transmit a second portion of the data on thescheduled return link resources (1154). In some aspects, the UT 900 mayreceive the grant for the scheduled return link resources prior to theexpiration of the time period, and may transmit a second portion of thedata on the scheduled return link resources during the time period. TheUT 900 may terminate data transmissions on the contention-basedresources in response to receiving the grant.

FIG. 12A shows an illustrative flowchart depicting an example operation1200 for receiving data from a UT via a satellite in accordance withexample implementations. The example operation 1200 may be performed bythe network controller 1000 depicted in FIG. 10. However, it is to beunderstood that operation 1200 may be performed by other suitabledevices capable of receiving data from a number of UTs (e.g., UTs 400)via one or more satellites (e.g., satellites 300 of FIG. 1).

First, the network controller 1000 may allocate contention-basedresources of the satellite system to a plurality of user terminals (UTs)(1202). In some aspects, the network controller 1000 may transmit anactivation signal on a physical forward-link control channel (PFCCH) toactivate the contention-based resources (1202A).

If the network controller 1000 has not granted PRSCH resources to theplurality of UTs, then the network controller 1000 may receive, from afirst UT via a satellite of the satellite system, a first portion ofdata on the contention-based resources (1204). The network controller1000 may also receive, from the first UT via the satellite, a bufferstatus report (BSR) (1206). In some aspects, reception of data and/orthe BSR from the first UT on the contention-based resources may operateas an implicit scheduling request for return link resources of thesatellite system.

The network controller 1000 may transmit a scheduling grant for thereturn link resources (1208). Then, the network controller 1000 mayreceive a second portion of the data on the granted return linkresources (1210).

The network controller 1000 may terminate the allocation ofcontention-based resources to the first UT (1212). In some aspects, thenetwork controller 1000 may terminate the contention-based resourcesbased on the scheduling grant (1212A). In other aspects, the networkcontroller 1000 may terminate the contention-based resources based on anexpiration of a time period selected by the RRC (1212B).

FIG. 12B shows an illustrative flowchart depicting an example operation1220 for receiving data from a UT via a satellite in accordance withexample implementations. The example operation 1220 may be performed bythe network controller 1000 depicted in FIG. 10. However, it is to beunderstood that operation 1220 may be performed by other suitabledevices capable of receiving data from a number of UTs (e.g., UTs 400)via one or more satellites (e.g., satellites 300 of FIG. 1).

First, the network controller 1000 may allocate contention-basedresources of the satellite system to a plurality of UTs (1222). In someaspects, the network controller 1000 may transmit an activation signalon the PFCCH to activate the contention-based resources (1222A).

If the network controller 1000 has not granted PRSCH resources to theplurality of UTs, then the network controller 1000 may receive, from afirst UT via a satellite of the satellite system, a first portion ofdata on a plurality of subframes of the contention-based resourcesduring a time period (1224). The network controller 1000 may receive,from the first UT via the satellite on the contention-based resources, abuffer status report (BSR) indicating an amount of data stored in abuffer of the first UT (1226). The network controller 1000 may thensuspend the allocation of the contention-based resources after anexpiration of the time period irrespective of collisions on thecontention-based resources (1228).

Then, the network controller 1000 may transmit a grant for the returnlink resources of the satellite system (1230). Thereafter, the networkcontroller 1000 may receive a second portion of the data on thescheduled return link resources after the expiration of the time period(1232).

FIG. 12C shows an illustrative flowchart depicting an example operation1240 for receiving data from a UT via a satellite in accordance withexample implementations. The example operation 1240 may be performed bythe network controller 1000 depicted in FIG. 10. However, it is to beunderstood that operation 1240 may be performed by other suitabledevices capable of receiving data from a number of UTs (e.g., UTs 400)via one or more satellites (e.g., satellites 300 of FIG. 1).

First, the network controller 1000 may allocate contention-basedresources of the satellite system to a plurality of UTs (1242). In someaspects, the network controller 1000 may transmit an activation signalon the PFCCH to activate the contention-based resources (1242A).

If the network controller 1000 has not granted PRSCH resources to theplurality of UTs, then the network controller 1000 may receive, from afirst UT via a satellite of the satellite system, a first portion ofdata on a plurality of subframes of the contention-based resourcesduring a time period (1244). Thereafter, the network controller 1000 maydetect a collision on the contention-based resources (1246). The networkcontroller 1000 may identify which of the plurality of UTs transmitteddata associated with the collision based on unique demodulationreference signal (DM-RS) shifts assigned to the plurality of UTs (1248).In response thereto, the network controller 1000 may request theidentified UT to re-transmit the data on the scheduled return linkresources (1250).

Then, the network controller 1000 may transmit a grant for the returnlink resources of the satellite system (1252). Thereafter, the networkcontroller 1000 may receive a second portion of the data on thescheduled return link resources after the expiration of the time period(1254). In some aspects, the network controller 1000 may receive are-transmission of the data, from the first UT, that was associated withthe detected collision (1256).

FIG. 13 shows an example user terminal or apparatus 1300 represented asa series of interrelated functional modules. A module 1302 for receivingdata for transmission to a gateway via a satellite may correspond atleast in some aspects to, for example, a processor as discussed herein(e.g., processor 920) and/or to a transceiver as discussed herein (e.g.,transceiver 915). A module 1304 for transmitting, during a time period,a first portion of the data on contention-based resources of thesatellite system may correspond at least in some aspects to, forexample, a processor as discussed herein (e.g., processor 920) and/or toa transceiver as discussed herein (e.g., transceiver 915). A module 1306for transmitting, during the time period, a scheduling request for thegrant of scheduled return link resources on a dedicated physical returnlink control channel (PRCCH) may correspond at least in some aspects to,for example, a processor as discussed herein (e.g., processor 920)and/or to a transceiver as discussed herein (e.g., transceiver 915). Amodule 1308 for terminating data transmissions on the contention-basedresources after an expiration of the time period or upon receiving thegrant of scheduled return link resources may correspond at least in someaspects to, for example, a processor as discussed herein (e.g.,processor 920) and/or to a transceiver as discussed herein (e.g.,transceiver 915). A module 1310 for receiving the grant for thescheduled return link resources may correspond at least in some aspectsto, for example, a processor as discussed herein (e.g., processor 920)and/or to a transceiver as discussed herein (e.g., transceiver 915). Amodule 1312 for transmitting a second portion of the data on thescheduled return link resources may correspond at least in some aspectsto, for example, a processor as discussed herein (e.g., processor 920)and/or to a transceiver as discussed herein (e.g., transceiver 915). Amodule 1314 for preventing additional data transmissions on thecontention-based resources may correspond at least in some aspects to,for example, a processor as discussed herein (e.g., processor 920)and/or to a transceiver as discussed herein (e.g., transceiver 915). Amodule 1316 for transmitting a buffer status report (BSR) on thecontention-based resources may correspond at least in some aspects to,for example, a processor as discussed herein (e.g., processor 920)and/or to a transceiver as discussed herein (e.g., transceiver 915).

FIG. 14 shows an example network controller or apparatus 1400represented as a series of interrelated functional modules. A module1402 for allocating contention-based resources of the satellite systemto a plurality of user terminals (UTs) may correspond at least in someaspects to, for example, a processor as discussed herein (e.g.,processor 1020) and/or to a transceiver as discussed herein (e.g.,transceiver 1015). A module 1404 for receiving, from a first UT via asatellite of the satellite system, a first portion of data on thecontention-based resources during a time period may correspond at leastin some aspects to, for example, a processor as discussed herein (e.g.,processor 1020) and/or to a transceiver as discussed herein (e.g.,transceiver 1015). A module 1406 for receiving, from the first UT viathe satellite, a scheduling request for return link resources on adedicated physical return link control channel (PRCCH) may correspond atleast in some aspects to, for example, a processor as discussed herein(e.g., processor 1020) and/or to a transceiver as discussed herein(e.g., transceiver 1015). A module 1408 for suspending the allocation ofthe contention-based resources after an expiration of the time period orupon a grant of scheduled return link resources may correspond at leastin some aspects to, for example, a processor as discussed herein (e.g.,processor 1020) and/or to a transceiver as discussed herein (e.g.,transceiver 1015). A module 1410 for transmitting the grant for thereturn link resources may correspond at least in some aspects to, forexample, a processor as discussed herein (e.g., processor 1020) and/orto a transceiver as discussed herein (e.g., transceiver 1015). A module1412 for receiving a second portion of the data on the scheduled returnlink resources may correspond at least in some aspects to, for example,a processor as discussed herein (e.g., processor 1020) and/or to atransceiver as discussed herein (e.g., transceiver 1015). A module 1414for transmitting, on a physical forward-link control channel (PFCCH), asignal for activating the contention-based resources may correspond atleast in some aspects to, for example, a processor as discussed herein(e.g., processor 1020) and/or to a transceiver as discussed herein(e.g., transceiver 1015). A module 1416 for receiving a buffer statusreport (BSR) on the contention-based resources may correspond at leastin some aspects to, for example, a processor as discussed herein (e.g.,processor 1020) and/or to a transceiver as discussed herein (e.g.,transceiver 1015).

The functionality of the modules of FIGS. 13 and 14 may be implementedin various ways consistent with the teachings herein. In some designs,the functionality of these modules may be implemented as one or moreelectrical components. In some designs, the functionality of theseblocks may be implemented as a processing system including one or moreprocessor components. In some designs, the functionality of thesemodules may be implemented using, for example, at least a portion of oneor more integrated circuits (e.g., an ASIC). As discussed herein, anintegrated circuit may include a processor, software, other relatedcomponents, or some combination thereof. Thus, the functionality ofdifferent modules may be implemented, for example, as different subsetsof an integrated circuit, as different subsets of a set of softwaremodules, or a combination thereof. Also, it will be appreciated that agiven subset (e.g., of an integrated circuit and/or of a set of softwaremodules) may provide at least a portion of the functionality for morethan one module.

In addition, the components and functions represented by FIGS. 13 and14, as well as other components and functions described herein, may beimplemented using any suitable means. Such means also may beimplemented, at least in part, using corresponding structure as taughtherein. For example, the components described above in conjunction withthe “module for” components of FIGS. 13 and 14 also may correspond tosimilarly designated “means for” functionality. Thus, in some aspects,one or more of such means may be implemented using one or more ofprocessor components, integrated circuits, or other suitable structureas taught herein.

Those of skill in the art will appreciate that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Further, those of skill in the art will appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the aspects disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the disclosure.

The methods, sequences or algorithms described in connection with theaspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor.

Accordingly, one aspect of the disclosure can include a non-transitorycomputer readable media embodying a method for time and frequencysynchronization in non-geosynchronous satellite communication systems.The term “non-transitory” does not exclude any physical storage mediumor memory and particularly does not exclude dynamic memory (e.g.,conventional random access memory (RAM)) but rather excludes only theinterpretation that the medium can be construed as a transitorypropagating signal.

While the foregoing disclosure shows illustrative aspects, it should benoted that various changes and modifications could be made hereinwithout departing from the scope of the appended claims. The functions,steps or actions of the method claims in accordance with aspectsdescribed herein need not be performed in any particular order unlessexpressly stated otherwise. Furthermore, although elements may bedescribed or claimed in the singular, the plural is contemplated unlesslimitation to the singular is explicitly stated. Accordingly, thedisclosure is not limited to the illustrated examples and any means forperforming the functionality described herein are included in aspects ofthe disclosure.

What is claimed is:
 1. A method of wireless communication in a satellitesystem, the method performed by a user terminal (UT) and comprising:receiving data for transmission to a gateway via a satellite; receiving,from the gateway, an activation of contention-based resources of thesatellite system; transmitting, during a time period, a first portion ofthe data on a plurality of subframes of the contention-based resourcesprior to receiving a grant of scheduled return link resources; andterminating data transmissions on the contention-based resources afteran expiration of the time period or upon receiving the grant ofscheduled return link resources, irrespective of collisions on thecontention-based resources.
 2. The method of claim 1, wherein theactivation comprises a signal received from the gateway via a dedicatedphysical forward link control channel (PFCCH) that is independent of thecontention-based resources.
 3. The method of claim 1, wherein theactivation indicates a modulation and coding scheme (MCS) to be used bythe UT when transmitting data on the contention-based resources.
 4. Themethod of claim 1, wherein the plurality of subframes of thecontention-based resources are allocated to the UT by a radio controllercircuit (RRC) associated with the gateway.
 5. The method of claim 1,wherein transmission of at least part of the first portion of the datacomprises an implicit scheduling request for the grant of scheduledreturn link resources.
 6. The method of claim 1, further comprising:transmitting a scheduling request, on a dedicated physical return linkcontrol channel (PRCCH) that is independent of the contention-basedresources, during the time period.
 7. The method of claim 6, wherein thePRCCH is allocated to the UT only between selected pairs of subframes ofthe contention-based resources.
 8. The method of claim 1, furthercomprising: receiving the grant for the scheduled return link resourcesprior to the expiration of the time period; transmitting a secondportion of the data on the scheduled return link resources during thetime period; and terminating data transmissions on the contention-basedresources in response to receiving the grant.
 9. The method of claim 1,further comprising: receiving the grant for the scheduled return linkresources after the expiration of the time period; and transmitting asecond portion of the data on the scheduled return link resourcesindicated by the received grant.
 10. The method of claim 1, furthercomprising: receiving, from the gateway, an indication of a collision onthe contention-based resources; and re-transmitting data associated withthe indicated collision on the scheduled return link resources after theexpiration of the time period.
 11. The method of claim 1, furthercomprising: triggering a buffer status report (BSR) in response toreceiving the data; and commencing the time period based on thetriggering of the BSR.
 12. The method of claim 11, further comprising:preventing additional data transmissions on the contention-basedresources until a subsequent BSR is triggered.
 13. The method of claim1, further comprising: commencing the time period based on transmissionof the data on a first of the plurality of subframes of thecontention-based resources.
 14. The method of claim 1, wherein the timeperiod is determined by a radio resource control (RRC) associated withthe gateway.
 15. The method of claim 1, wherein the contention-basedresources are shared between a plurality of UTs during the time period.16. The method of claim 15, wherein each of the plurality of UTstransmits data on the contention-based resources using a uniquedemodulation reference signal (DM-RS) shift selected by a schedulerassociated with the gateway.
 17. A user terminal (UT) configured forwireless communication in a satellite system, the user terminalcomprising: one or more processors; and a memory storing instructionsthat, when executed by the one or more processors, cause the userterminal to: receive data for transmission to a gateway via a satellite;receive, from the gateway, an activation of contention-based resourcesof the satellite system; transmit, during a time period, a first portionof the data on a plurality of subframes of the contention-basedresources prior to receiving a grant of scheduled return link resources;and terminate data transmissions on the contention-based resources afteran expiration of the time period or upon receiving the grant ofscheduled return link resources, irrespective of collisions on thecontention-based resources.
 18. The user terminal of claim 17, whereinthe activation comprises a signal received from the gateway via adedicated physical forward link control channel (PFCCH) that isindependent of the contention-based resources.
 19. The user terminal ofclaim 17, wherein the activation indicates a modulation and codingscheme (MCS) to be used by the UT when transmitting data on thecontention-based resources.
 20. The user terminal of claim 17, whereinthe plurality of subframes of the contention-based resources areallocated to the UT by a radio controller circuit (RRC) associated withthe gateway.
 21. The user terminal of claim 17, wherein transmission ofat least part of the first portion of the data comprises an implicitscheduling request for the grant of scheduled return link resources. 22.The user terminal of claim 17, wherein execution of the instructionscauses the user terminal to further: transmit a scheduling request, on adedicated physical return link control channel (PRCCH) that isindependent of the contention-based resources, during the time period.23. The user terminal of claim 22, wherein the PRCCH is allocated to theUT only between selected pairs of subframes of the contention-basedresources.
 24. The user terminal of claim 17, wherein execution of theinstructions causes the user terminal to further: receive the grant forthe scheduled return link resources prior to the expiration of the timeperiod; transmit a second portion of the data on the scheduled returnlink resources during the time period; and terminate data transmissionson the contention-based resources in response to receiving the grant.25. The user terminal of claim 17, wherein execution of the instructionscauses the user terminal to further: receive the grant for the scheduledreturn link resources after the expiration of the time period; andtransmit a second portion of the data on the scheduled return linkresources indicated by the received grant.
 26. The user terminal ofclaim 17, wherein execution of the instructions causes the user terminalto further: receive, from the gateway, an indication of a collision onthe contention-based resources; and re-transmit data associated with theindicated collision on the scheduled return link resources after theexpiration of the time period.
 27. The user terminal of claim 17,wherein execution of the instructions causes the user terminal tofurther: trigger a buffer status report (BSR) in response to receivingthe data; and commence the time period based on the triggering of theBSR.
 28. The user terminal of claim 27, wherein execution of theinstructions causes the user terminal to further: prevent additionaldata transmissions on the contention-based resources until a subsequentBSR is triggered.
 29. The user terminal of claim 17, wherein executionof the instructions causes the user terminal to further: commence thetime period based on transmission of the data on a first of theplurality of subframes of the contention-based resources.
 30. The userterminal of claim 17, wherein the time period is determined by a radioresource control (RRC) associated with the gateway.
 31. The userterminal of claim 17, wherein the contention-based resources are sharedbetween a plurality of UTs during the time period.
 32. The user terminalof claim 31, wherein each of the plurality of UTs transmits data on thecontention-based resources using a unique demodulation reference signal(DM-RS) shift selected by a scheduler associated with the gateway.